GENETICS

Fertilization

• Fertilization (syngamy) is the _______ of two haploid

gametes (the sperm and the egg) to form a

_________(2n) zygote.

• Since human males produce X-bearing and Y-

bearing sperm, and human females produce only

X-bearing eggs, the gametes combine

___________according to the following table:

fusion

diploid

randomly

• The male (XY) and female (XX) offspring in the above

table are in a________ ratio with an _______number of

boys and girls. Therefore, the chance of having a boy is

1/2 or ______and the chance of a girl is also 1/2 or _____

Gametes X-bearing

sperm

Y-bearing

sperm

X-bearing egg

X-bearing egg

XY

XX XY

XX

50-50 equal

50% 50%.

Meiosis vs. Mitosis• __________is the division of a haploid (n) or diploid

(2n) cell into _____duplicate ____________ cells. In a strict definition, mitosis (karyokinesis) refers to the division of a nucleus into two duplicate nuclei, each with____________ sets of chromosomes.

• __________is a special kind of cell division in which the chromosome number is______________ in half. This is how the chromosome number in a life cycle changes from__________ (2n) to _________(n). In humans, the only cells that undergo meiosis are ______ cells in the ovaries and _________cells in the testes.

Mitosistwo daughter

identical

Meiosisreduced

diploid haploid

egg sperm

• Meiosis is used in____________ reproduction of

organisms to combine male and female, through

the sperm and egg, to create a new, __________

biological organism.

• Mitosis is used by ___________________organisms to

reproduce asexually, or in the organic __________of

tissues, fibers, and membranes. __________versions of

cells can be created to form tissues through Mitosis.

sexual

single

single-celled

growth

Identical

Haploid vs. DiploidDiploid cells contain ___________________________ of chromosomes.

Haploid cells have _________________________________

as diploid i.e. a haploid cell contains only

___________________________________________

two complete sets (2n)

half the number of chromosomes (n)

one complete set of chromosomes

A Diagram Comparing Mitosis and Meiosis

Complete table of missing information p. 6

somatic Gametes/ sex cells

1 2

2

1 1

4

Create gametesCreate identical cells

2n (46) 2n(46)

1n (23)2n (46)

2n (46)

Body cells Sex cells

Mendel’s Principles

The story of Gregor Mendel and his work provides a

fascinating glimpse into the nature of science.

Mendel was born in 1822 and as a young man

attended the University of Vienna. There he studied

chemistry, biology, and physics, but left before

graduating, probably for health reasons. He entered

the Augustinian monastery in Brno, and with the

support of the abbot, began his investigation of the

inheritance of certain traits in pea plants (Pisum

sativum). His choice of pea plants as the

experimental subject was excellent as peas grow and

reproduce quickly, their mating can be controlled,

and the plants have a number of distinct traits thatare readily observed.

Over the course of the next 8 years,

Mendel conducted experiments and

maintained detailed records of his results.

His university training led him to design

simple experiments that permitted him to

observe the inheritance of one trait at a

time. His use of mathematics allowed him

to formulate conclusions based on his

results. These conclusions are known as

Mendel’s Laws or Principles.

The Different traits Mendel Studied:

In 1865, Mendel presented his findings in a

paper entitled “Experiments in Plant

Hybridization” at a meeting of the Association

for Natural Research in Brno. The paper was

published in the Proceedings of the Brno

Society of Natural Science in 1866. Mendel’s

work was ground breaking, not only for his

discoveries in genetics, but also for his use of

mathematical and statistical analysis as a

means for interpreting his results.

The scientific community of the time did not seem to grasp

the significance of Mendel’s work. As a result, it was largely

ignored. Mendel abandoned his research upon his

election as abbot in 1868, due in part to his heavy

workload, as well as the lack of recognition for his

research. Gregor Mendel died in 1884 never knowing if the

world would acknowledge the importance of his work. In

1900, three scientists working independently rediscovered

and confirmed Mendel’s laws of heredity. Hugo de Vries,

Carl Correns and Erich von Tschermak-Seysenegg gave

credit to Gregor Mendel in the publications of their papers,

thereby giving him the recognition he long deserved.

Mendel’s Principles of Inheritance

1. Inherited traits are transmitted by genes which

occur in alternate forms called alleles i.e. genes

come in pairs.

2. Principle of Dominance – when 2 forms of the same

gene are present the dominant allele is expressed. A

heterozygous genotype will express the dominant

allele. For example, Pp will express purple flowers

because P is dominant to p.

3. Principle of Segregation – in meiosis two alleles

separate so that each gamete receives only one form

of that gene.

4. Principle of Independent Assortment – separate

genes for separate traits are passed independently of

one another from parents to offspring.

Genetics

______________all the characters transmitted from

parent to offspring. ____________is the study of

heredity. A __________________ (or trait) any aspect

of an individual that can be described.

ex:

Heredity

Genetics

characteristic

Curly hair

Short

Blue eyes

All individuals of the same species have in

common a number of characteristics. For

mankind these characteristics are:

There are individual characteristics that come

from parents

ex:

Walking upright

Opposable thumb

Complex brains

Curly hair

Brown eyes

Genetics• Children inherit genes

that control specific

traits from their parents.

We now know that

genes are parts of a

______________and that

DNA is package in

____________________

DNA molecule

chromosomes

Genetics• Therefore, when we talk about genes being

inherited from one generation to the next, we are

really talking about how the gene-carrying

chromosomes behave during ____________and

________________.

Question: Based on your understanding of meiosis, fertilization and mitosis, explain why each cell in a

person has two copies of each gene, one copy from

his or her mother and one copy from his or her father

meiosis

fertilization

• To understand how specific genetic traits are

inherited, we will consider the example of the gene

which controls whether the bottom of the earlobe

hangs free or the bottom of the earlobe is attacheddirectly to the head.

• First, look at your classmates to see whether you

can find examples of attached earlobes and

earlobes which hang free.

• There are two different ________________ for this

gene. The allele which codes for earlobes which

hang free is symbolized by ____, and the allele

which codes for attached earlobes is symbolized by

____. We’ll analyze inheritance for the case where

each parent has one E allele and one e allele (i.e.

both parents are Ee). What combinations of E

and/or e alleles would you expect to observe in the

children of these parents?

alleles

E

e

Biologists use the _______________________(shown

below) to answer this type of question. This Punnett

Square shows that, as a result of meiosis _________ of

the father’s sperm will have a chromosome which

carries the E allele, and _________ will have the

chromosome with the e allele. Similarly, ________ of the

mother’s eggs will have an E allele and ____________ will

have an e allele.

Punnett Square

halfhalf

half

half

• The _______smaller squares within the larger Punnett

Square show the possible genetic combinations

resulting from fertilization of the two different types

of_________ by the two different types of_________

E e

E

e

sperm

eggs

four

eggs sperm.

EE

Ee

Ee

ee

1. What proportion of this couple’s children would you

expect to be EE?

2. What proportion of this couple’s children would you

expect to be ee?

3. What proportion of this couple’s children would you

expect to be Ee?

4. Will EE children have earlobes which hang free or are

attached? What about ee? What about Ee?

1/4

1/2

1/4

Genetics• Homozygous:_____________________________________

• __________

• Heterozygous:____________________________________

• _____

When there are 2 identical alleles

for a trait.

When there are 2 different alleles for a

trait.

Genetics• Often, one allele in a heterozygous pair of alleles is

______________and the other is___________. This

means that the dominant allele __________________

__________________________________________________

• ___________

• Typically, the dominant allele is symbolized by a

___________letter (E) and the recessive allele is

symbolized by a_________________ letter (e).

dominant recessive

determines the

observable characteristic of the heterozygous

individual.

capitallower-case

• Each human inherits ______________________________

(x-somes) from each parent, for a total of _______

chromosomes.

• Each chromosome has many ___________ (sections of

DNA that code for specific proteins).

• You inherit 2 genes for every trait you have, one

gene from each parent.

E.g. Trait → tongue rolling

R – roller gene

r – non-rolling gene

23 chromosomes

46

genes

Genetics• Each member of this gene pair is called an________.

• R – is called the_______________ allele as it will express

its trait whenever it appears.

• r – is called the ____________allele and it can only

express its trait when no other genes are present

except its own kind.

allele

dominant

recessive

• PHENOTYPE

• Term given to the

expression of the genes

• i.e. what it makes you

look like

• Roller or non-roller

• GENOTYPE

• Term given to the 3

combinations the 2

different genes can

occur in.

• i.e. either homozygous

dominant,

heterozygous or

homozygous recessive

• E.g. RR, Rr, rr

• __________________– Is what you use to__________

the outcome of crossing various genotypes. If you

know the genotypes of the parents, you can use a

Punnett square to predict the possible genotypes of

their offspring.

Punnett Square predict

Do general questions p.17.

Mendel’s Monohybrid Crosses

• A____________ is the offspring of parents that have

______________forms of a trait, such as tall and short

height. A monohybrid cross means “______” and the

two parents differed from each other by a single–

______________height.

hybrid

different

one

gene (allele)

Mendel’s Monohybrid Crosses

Pure bred parents

• Each parent has two ____________alleles for a single

trait.

• E.g.

Hybrid Parents

• Each parent has two ___________alleles for a single

trait.

• E.g

identical

PP or pp

different

Pp

F1 generation

• First generation following the breeding of oppositely pure bred parents

• Results in offspring that are all ______________

F2 generation

• Second generation following initial breeding of pure bred parents

• Offspring are from __________________hybrid F1 generation

• Results in a ________ ratio of phenotypes

• Do Matching Definitions p. 19

hybrid

inter-breeding

3:1

• Do matching definitions

• Do Monohybrid Problems 1 p. 22-23

• Do Monohybrid Problems 2 p. 23-24

Test Cross• Breeding of an organism of ____________genotype

with a homozygous _____________individual to

determine the unknown genotype.

• E.g.

unknownrecessive

P = purple, p = white

F1 generation = all purple. What is the

unknown genotype of the purple

parent?

Dihybrid Cross• A breeding experiment in which parental varieties

differing in _______traits are mated.

• E.g. ___________________________________________________

BbSs x BbSs

• Do large Punnett Square on the whiteboard →

Method 1

• Example on p. 25-26 → Method 2

• Do Dihybrid Cross Worksheet p. 27

twoBlack, short fur guinea pig x black, short fur pig

Co-Dominance

• Both alleles are _________expressed in the phenotype.

The “co” in co-dominance means “______________”

• Both alleles are ____________dominant

• F2 genotype and phenotype ratios are _________

• Analogy on whiteboard

clearlytogether

equally

1:2:1

• Example: M, N and MN blood groups in humans.

• People in M group have one type of molecule on

their red blood cells.

• People in N group have a different type of

molecule on their red blood cells.

• People in MN group have both M and N

molecules on their red blood cells.

Genotype Phenotype

LMLM M

LMLN MN

LNLN N

ROAN COW (RW)

Do Co-Dominance

Practice Problems p.32

Incomplete Dominance• F1 hybrids have an appearance that is __________

between the phenotypes of the parental varieties.

• Neither allele is _____________

• F2 phenotypic and genotypic ratios are ______

• There are 2 ways to recognize incomplete

dominance:

o Notice that the offspring is showing a _______

phenotype. The parents each have one, and the

offspring are different from the parents.

o Notice that the trait in the offspring is a ________

(mix) of the parental traits.

blended

dominant

1:2:1

3rd

blend

• Example: Snapdragon flower color

ww (white) rw (PINK)!! rr (Red)

Do Incomplete Dominance Practice Problems p. 34

(rr) (ww)

(rw)

(rw) (rw)

1 (rr): 2(rw): 1(ww)

1 red: 2 pink: 1 white

Lethal Genes• The offspring that receive _________________________

alleles are unable to sustain life.

• E.g. Tay-Sachs Disease

homozygous recessive

What have you learned so far? Entrance Slip

1. What did you find most interesting last unit?

2. How does Genetics apply to the real world?

Human Genome Project?

1. What are the implications of having your genome

mapped out?o Screen for gene(s) that cause disease

o Create your “ideal” baby

o Carry your sequenced genome on a chip with you that everyone

(doctors, employers, insurance agencies) has access to

2. Would you sequence YOUR genome? Why?

Multiple Alleles

• Genes that can exist in populations in _______than two

_______________

• E.g. ABO blood groups in human.

o There are_____possible phenotypes: ____________

o There are ___different alleles for one gene_________

o There _____are genotypes possible.

o Both A and B are dominant to the O allele.

alleles

4 A, B, AB, O

3 A, B, O

6

more

o AA has blood type ____.

o AO has blood type ____.

o BB has blood type ____.

o BO has blood type ____.

o AB has blood type ____ (co-dominant).

o OO has blood type ____.O

B

A

A

B

AB

IA and IB alleles are co-dominant only io io genotype gives

the O blood type. O group is the lack of A or B.

The blood type can be used to help determine paternity,

but we cannot be certain.

eg. A male type B may be the father of a child of O

blood type (genotype of would be IBio), but if the male is

type AB, he cannot possibly be the father.

The Rh factor is transmitted separately for

types A, B, AB or O. It is Rh + (Rh positive) if

the Rh factor is present on the red blood cells

and Rh- if the factor if is absent.

Were the babies switched?

Is it possible for Michael and Danielle to have a child who has type O blood?

How do you know this?

Was a switch made at the hospital?

Do Blood type problems p.5

**NOT IN

NOTES **

Epistasis

• One locus_________ the phenotypic _______________

at a second locus.

• E.g. coat colour in Labrador Retrievers.

o Black coat is dominant to brown coat which is

represented by ______.

o To have a brown coat the dog must be _______

o A second gene locus determines whether hair

pigment is deposited at all.

alters expression

B, b.

bb

o Colour (EE or Ee) is ______________ and no pigment

(ee) is __________________.

o If the dog is homozygous recessive for coat

colour, ee, then the coat is yellow regardless of

genotype at the black/brown locus.

o _____________in humans or in other animals is

another example. If an individual inherits aa alleles

that cause albinism (inability to produce the

pigment melanin), whatever the genotype

responsible for eye color or hair color, because it

can only be expressed if the individual is an

albino.

dominant

recessive

Albinism

NOT IN NOTES

See board

Modifier Gene

A ________________ can intervene in the phenotypicexpression of an allele on a different locus. In theHolstein breed (like cow) the distribution of the spotsare due to a single pair of alleles but the relative amountof black and white spots is controlled by modifier genes.

modifier gene

Polygenic Inheritance

• An _____________ effect of two or more genes on a single

phenotypic character.

• E.g. skin pigment in humans.

• It is controlled by three separately inherited genes (A, B,

C).

o Each A, B, C contribute one “unit” of darkness to the

phenotype and are incompletely dominant to a, b, c.

o _____________person would be very dark.

o _____________person would be very light.

o _____________person would be an intermediate.

o Alleles have a cumulative effect; genotypes AaBbCc

and AABbcc would make the same darkness.

additive

AABBCC

aabbcc

AaBbCc

Linkage• Genes located on the same chromosomes tend

to be inherited _______________ because the

chromosome is passed along as a _________.

• These genes are said to be _________.

• E.g. wing colour and wing size in fruit flies.

• E.g. hair color and freckles

together

unit

linked

Crossing-over• When two homologous chromosomes pair during

meiosis, the chromatids can ______________________.

This is a random phenomenon that can occur

anywhere along the chromosome except almost

near the centromere. This means that a crossover is

more likely to occur between genes distant from

each other on a chromosome than between

closely spaced genes.

exchange fragments

http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0ahUKEwjNx46Rhr_OAhXFOyYKHdS3AXQQjRwIBw&url=http://www.yourarticlelibrary.com/biology/notes-on-the-process-and-mechanism-of-crossing-over/12069/&psig=AFQjCNFIuh4_c4QPnbRhv2iOvRu2QLXWzQ&ust=1471200243396819

Sex Determination

• Henry VIII of England

married six times in an

attempt to have a

legitimate male heir to the

English throne. Recalling

your knowledge of Grade 9

Science, do you think Henry

was correct in blaming his

wives for their inability to

produce a son? (Henry did

eventually have one son,

who inherited the throne

after his father’s death.)

Sex-Linked Genes

Autosomes: ____________________________________________

_______________

Sex Chromosomes: _______________________________

The human has 46 chromosomes divided into 23 pairs including 22

homologous pairs, the 23rd pair determines sex.

Chromosome X or Y

All the chromosomes (1-22) except the sex

chromosomes

Sex Determination

• Female _______, Male ________

• Sex chromosomes segregate during meiosis, and

each gamete receives one

o Each ovum contains 1 ____ chromosome.

o ½ the sperm cells contain an ____ and ½ contain

a ____ chromosome

• Sex determination is a matter of chance, __________

• SRY gene (located on the Y chromosome) is

required for the development of ___________. In its

absence, the gonads develop into _______________.

XX XY

X

X

Y50/50

testes

ovaries

Sex Determination

• Sex-Linked Genes: ________________________________

__________________________________

• Fathers pass X-linked alleles to all of their

_________________, but none of their ____________.

• Mothers can pass sex-linked alleles to _________ sons

and daughters.

• Carrier: ___________________________________________

__________________________________________

____________________________________

• A carrier is normal but can pass on the harmful allele

to the offspring.

a gene that is located on the X or

Y chromosome. Most are on the X

daughters sons

both

An individual who is heterozygous at a

given locus, with one normal and one

potentially harmful recessive allele

Boys will have a 50% chance of

inheriting the disorder. None of their girls

will have it, but half of them are likely to

be carriers.

Examples

Female Carrier x Normal Male

All of their girls will be carriers. None of

their boys will inherit the harmful

allele. Only girls receive X

chromosomes from their fathers.

2. Normal Female x Male with X-linked recessive

disorder

Sex-Linked Gene Examples• Muscular dystrophy

o Duchenne MD

o Becker MD

o Emery-Dreifuss MD

o Other forms that are autosomal instead of X-linked

• Hairy ears: The gene for hairy ears is found only on the Y

chromosome (Y-linked). Therefore, males are the only ones to have

this sex-linked gene.

• Color-blindness: The gene for color blindness is X-linked and is recessive. This means that it affects

more males than females.

Hemophilia: Hemophilia is a rare bleeding disorder in which the blood doesn’t clot normally. Like color-

blindness, the gene for hemophilia is recessive and is X-

linked. This means that males are more likely to be

affected than females.

*The effect of Hemophilia on Queen Victoria and her

family*

** Some genes located on autosomes are expressed differently

from one sex to another, probably because of hormonal

differences. For example baldness in humans. **

Do example on

board and sex-

linked problems

p.15

Pedigree AnalysisIntroduction

A ______________ is a diagram of family relationships that

uses symbols to represent people and lines to represent

genetic relationships. Its purpose is to analyze the pattern

of inheritance of a particular trait.

These diagrams make it easier to visualize ____________

within families, particularly large extended families.

Pedigrees are often used to determine the mode of

___________________ (dominant, recessive, etc.) of genetic

diseases. A sample pedigree is below.

pedigree

relationships

transmission

To facilitate comparison between family trees, geneticists

employ several symbols when they make a family tree.

In the exercises below, assume that the trait in

question is a genetic disease or abnormality. We

will learn patterns of inheritance that have the

following modes of inheritance:

• Autosomal dominant

• Autosomal recessive

• Sex-linked recessive

Autosomal Dominant

A?

aa aa

aa

Aa

Aaaa

aa

aa

Aa Aa

AA or Aa

Autosomal Recessive

aa → Not Possible!!!

aa aa

aa aa

aa aa aa aa

aa

Aa Aa

AA or Aa

aa Aa most likely

Aa Aa Aa Aa or AA

Aa Aa AA or Aa

aa AA or Aa aa AA or Aa

X-Linked RecessiveXaXa

XAY

XaY → Not Possible!!!

XaXa

XaY

XAY

XaXaXAY

XAXa

XaXa XAY

XaXa→ Not possible!!!

XAXa XaY

XaY

XaXa XaY

XaXa→ Not Possible!!!

Interpreting a Pedigree1. Is it Autosomal or X-linked?

• If most of the males in the pedigree are affected → X-linked

• If it is a 50/50 ratio between men and women→ autosomal

2. Is it Dominant or Recessive?

• If dominant – one of the parents must

have the disorder

• If recessive – neither parent has to

have the disorder because they can

be heterozygous

1 2 3 4 5 6 7 8 9 10

1 2

I

1 2 3 4 5 6

II

III

Dominant Autosomal Pedigree

Recessive Autosomal Pedigree

Do Application of Pedigree analysis p.28-29

Examples of Autosomal Dominant Disorders• Dwarfism

• Polydactyly and Syndactyly

• Hypertension

• Hereditary Edema

• Chronic Simple Glaucoma – Drainage system for fluid in the eye does not work and pressure builds up, leading to damage of the optic nerve which can result in blindness.

• Huntington’s Disease – Nervous system degeneration resulting in certain and early death. Onset in middle age.

• Neurofibromatosis – Benign tumors in skin or deeper

• Familial Hypercholesterolemia – High blood cholesterol and propensity for heart disease

• Progeria – Drastic premature aging, rare, die by age 13. Symptoms include limited growth, alopecia, small face and jaw, wrinkled skin, atherosclerosis, and cardiovascular problems but mental development not affected.

Examples of Autosomal Recessive Disorders

• Congenital Deafness

• Diabetes Mellitus

• Sickle Cell anemia

• Albinism

• Phenylketonuria (PKU) – Inability to break down the amino acid phenylalanine. Requires elimination of this amino acid from the diet or results in serious mental retardation.

• Galactosemia – enlarged liver, kidney failure, brain and eye damage because can’t digest milk sugar

Examples of Autosomal Recessive Disorders

• Cystic Fibrosis – affects mucus and sweat glands, thick mucus in lungs and digestive tract that interferes with gas exchange, lethal.

• Tay Sachs Disease – Nervous system destruction due to lack of enzyme needed to break down lipids necessary for normal brain function. Early onset and common in Ashkenazi Jews; results in blindness, seizures, paralysis, and early death.

Examples of Sex-Linked Recessive Disorders

• Red/Green Colorblindness – Difficulty perceiving differences between colors (red or green, blue or yellow).

• Hemophilia – Absence of one or more proteins necessary for normal blood clotting.

• Deafness

• Cataracts – opacity in the lens that can lead to blindness

• Night blindness – (Nyctalopia) rods do not work so that can not see in the dark

• Glaucoma – pressure in the eye that can lead to optic nerve damage and blindness

• Duchenne Muscular Dystrophy – progressive weakness and degeneration of skeletal muscles that control movement due to absence of dystrophin (protein that maintains muscle integrity). Mainly in boys, onset 3-5 yrs, by 12 years can’t walk, and later needs respirator.

Genetic Testing – Ethical Issues

Recent advances in genetics have raised ethical

questions regarding the screening of individuals for

inherited conditions and disorders. DNA screening,

biochemical tests, amniocentesis, and family pedigree

analysis are all tools that genetic counselors use. Some

tests may be performed on individuals and others on

fetuses.

These tools are used by genetic counselors to analyze

the risk to individuals for developing a disorder, or the risk

of passing on a known inherited disorder or condition to

offspring. Genetic counselors can present options to

parents so that potential risks can be avoided or

reduced.

• There are many issues to be considered in genetic

testing. Are tests equally available to all

Manitobans, or only to those with the money to pay

for the tests, or to those who live in larger urban

centers? Should genetic testing for a disorder be

performed on individuals for whom there is no

available treatment (e.g. Huntington disease)? Do

third parties (e.g. insurance companies, employers)

have the right to genetic test results?

• Question:

• You know that an inherited genetic condition runs in

your family. Given the opportunity, would you be

tested to determine whether you carry the gene?

•

Chromosomal Mutations• _________________ – A section of a chromosome breaks

away and then flips over or inverts before it reattaches.

• __________________ – A section of a chromosome breaks

away and then reattaches to another chromosome.

• __________________ - A section of a chromosome breaks

away and then simply disappears.

• ____________________- The section of chromosome that

breaks away, reattaches to the homologous

chromosome.

• ** All four of these mutations can cause abnormalities in

the individual.

Inversion

Translocation

Deletion

Duplication

• ______________– This is a condition in which the cells of

the individual contain extra sets of chromosomes. This is

very common in plants.

• _________________– absence of a chromosome or the

presence of an extra chromosome caused by non-

disjunction.

Individual with Down syndrome - trisonomy 2n +1

Individual monosomic – monosomy 2n -1

Non-disjunction, giving too much or not enough chromosomes to gametes may occur during

A) anaphase I or B) anaphase II.

•

Polyploidy

Aneuploidy

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwi1xvX_nb_OAhWJ4iYKHQVqA24QjRwIBw&url=http://intranet.tdmu.edu.ua/data/kafedra/internal/distance/classes_stud/English/1course/Medical%20Biology,%20Parasitology%20and%20Genetics/3.%20Variation%20in%20human%20beings.%20Methods%20of%20research%20of%20human%20heredity..htm&bvm=bv.129422649,d.dmo&psig=AFQjCNFQ8_wHNupD5aDkmB4l_cdtio30VQ&ust=1471206577672966

Several Common Syndromes are

caused by Nondisjunction• Down syndrome: present in about 1 in 800 children

born in Canada. All persons with Down syndrome

have _______genetic material associated with the

_______chromosome________________.

• Turner syndrome: present in about 1 in every 2500 _______ born in Canada. All girls with Turner

syndrome are __________or have a _______________

• _______________(XO).

• Klinefelter syndrome: present in about 1 in every

1000 _______born in Canada. All boys with Klinefelter

syndrome carry an __________________________

extra21st (trisomy 21)

girls

missing damaged X

boys

extra chromosome (XXY).

chromosome

Tests to Examine Chromosomes

Amniocentesis - a needle is used to withdraw fluid from the uterus which contains fetal cells

Chorionic Villi Sampling - a suction tube inserted into the vagina removes fetal cells

*Tests are not usually performed due to risk of

spontaneous abortion*.

Karyotyping_____________- A picture of a person's chromosomes,

arranged by size and grouped into homologous pairs.Karyotype