Guided Notes: Meiosis

Mitosis Meiosis Mitosis is a form of __________________

reproductiono This means it only requires _______

organism! (ex:___________________)o For growth and repair of _________

(body) cellso Results in _____ cells ___________ to

the parent cell

Recall that DNA is condensed into _________o Humans have a total of ______

chromosomes per cell (23 pairs) ___ of the pairs are _________

present in all ___ par is a ____ chromosomes

(XX or XY)

When mitosis occurs, each new cell will have _____ chromosomes, just like the original!

The cells produced by mitosis are _________; diploid cells contain two complete sets (____) of chromosomes

Meiosis is a form of __________________ reproduction

o This means it takes _____ organisms to make a new organism

o Results in _______ cells that are ______________ to the parent cell

o These daughter cells are called __________ (sperm and egg cells)

There are 2 phases in meiosiso In _____________, the cell divideso In _____________, the cell divides

again, creating 4 cells

Cells produces in meiosis are ___________: haploid cells contain ______ the number of chromosomes as diploid (n)

When meiosis occurs, each new cell will have ______ chromosomes, half the original!

The _______ gametes (n) fuse during fertilization to make a ________ cell (2n)

o This new cell is called a _________, and will grow into a new organism

Comparing Mitosis and MeiosisMitosis Meiosis

Type of Reproduction

Purpose

Number of Divisions

Number of Cells Produced

Genetic Diversity

Meiosis is important because it leads to greater _______________________ Genetic diversity is important because….

o Groups with ____________ genetics have a greater chance to survive Example:___________________________________________________________

______________________________________________________________o Genetic diversity reduces incidence of ________________ traits

Example: ________________________________________________________________________________________________________________________

Sources of Genetic Variation Include:1) _________________________________________________2) _________________________________________________3) _________________________________________________4) _________________________________________________

The process of _______________ and the ____________ assortment of chromosomes during meiosis make genetic variation possible

_____________________ produces the greatest amount of variation!

Sources of Genetic Variation

Independent Assortment

Independent assortment produces 2n distinct gametes, where n=___________________________

Example: In humans, n= _____, and 223=________________

o That’s a lot of diversity!Crossing Over During Meiosis, the

____________________________ (a set of 1 maternal and 1 paternal) undergo a process called _____________________

This is the exchange of _________ material between _________________

Gene Mutation Mutations can cause variations in genes

by introducing _______________ into a population

Mutations that can be passed down are those _____________ (sperm and egg cells)

Other mutations, such as tobacco smoke altering lung cells, cannot be passed down

Nondisjunction= the failure of homologous chromosomes or sister chromatids to __________correctly during cell division

Guided Notes: Simple GeneticsPunnett Squares

In order to determine the ___________ a person might inherit, we use a simple diagram called

a ____________________________

o Give us _________________ of an offspring having particular traits

Pieces of the Punnett Square

Allele: A _____________ form of a ______________

o Humans inherit __________ allele from each parent that determines a ___________

o Ex. Curly/straight hair, tall/short, etc.

Dominant Allele: A ____________allele shows their effect even if there is only ______ copy

of the allele (think strong!)

o Dominant alleles are denoted by a capital letter (Ex. _________)

Recessive Allele: A ___________allele will only show up if no dominant alleles are in place.

(think weak!)

o Recessive alleles are denoted by a lower case letter (Ex. ________)

Dominant and recessive alleles pair together to determine a ___________! (Ex. ___________)

Homozygous: If both letters are ____________ (both dominant (capital) or both recessive

(lowercase)), the alleles are ____________________

o “Homo” means “_________”

o Ex. Let’s say “A” represents the allele for a widow’s peak, and “a” represents the allele

for a straight hairline

A person with “AA” would be called homozygous __________________

A person with “Aa” would be called homozygous __________________

Heterozygous: If both letters are ______________ (one dominant (capital) and one recessive

(lowercase)), the alleles are ______________________

o “Hetero” means “__________________”

o Ex. A person with “Aa” would be heterozygous

Would they have a widow’s peak or a straight hairline?

Genotype: The ________________, _______________ information of an organism

o Example: A person’s genotype is Aa (heterozygous); they can pass on either a

dominant allele or a recessive one

Phenotype: The _____________,_______________ appearance of an organism

o Example: A person has a widow’s peak

Building a Punnett Square

Consider the following alleles for color of a pea plant:

AA (Yellow-homozygous dominant)

Dominant or Recessive? Heterozygous or Homozygous Phenotype or Genotype?

A _______________ AA ____________________ She’s homozygous recessive ________

b _______________ Bb ____________________ She has blue eyes _________________

B _______________ cc _____________________

Aa (Yellow-heterozygous)

aa (Green-homozygous recessive)

Problem: Let’s say you had two pea plants, both heterozygous yellow (Aa), and you wanted to

know what color plants would be produced. How would you find out? ____________________

A Few Notes on Genetics:

1. Setting up the squarea. What we know: ____________________

b. So, cross _________________ will be carried out in the

Punnett Square

2. Carrying out the squarea. Father’s letters cross to the __________

b. Mother’s letters cross ____________

c. Notice each combination has one allele from dad and one

from mom

3. Interpreting the final squarea. Once the square is finished, determine the _____________

and ____________ ratios of the possible offspring

i. Genotype:

ii. Phenotype: What is the probability of producing offspring that have short whiskers from a cross of two long whiskered seals, one homozygous dominant and one heterozygous?

Genotype: Genotype:

Phenotype: Phenotype:

Tt x tt

Some traits are controlled by _______________________ pair of genes, and so present a

wide range of phenotypes (ex. Skin, hair, eye color)

All traits depend on both _______________ and _____________ factors

o Heredity determines your traits, but the environment may play a role in how they act

Guided Notes: Genetic Diseases

Dominant or Recessive?

If a disease is ___________________, both parents have to pass on a mutated allele to the

offspring

o Those who are heterozygous (Aa) are ____________, meaning they have the mutated

allele and can pass it on, but are ____________ themselves

If a disease is ___________________, only one parent has to pass on the mutated allele for

offspring to have it

o Can a person with a dominant disease be a carrier?

Genetic Diseases

Disease Dominant or Recessive? CharacteristicsCystic Fibrosis Causes __________ buildup in lungs

and digestive system

Those affected have _______________

and ____________________________

Common in those with _____________

ancestry

Life expectancy up to _____ years

thanks to ___________________

Sickle Cell Anemia Affects a person’s _________________

cells

The “sickle” or bent shape causes the

cells to get stuck in ________________

Common in those with _____________

ancestry

Carriers associated with ____________

resistance

PKU Stands for _______________________

Missing the ____________to break

down phenylalanine, an amino acid

Results in __________ deterioration

People affected must keep low

____________ diet + inject enzyme

Huntington’s

Disease

Affects the _____________ of the body

Affected will have _________________

decline

Often does not show signs until a

person reaches mid _________

A woman is concerned that she may develop Huntington’s Disease because her father has it. What is the probability that she has Huntington’s?

A woman who is a carrier for Cystic Fibrosis marries a man who is also a carrier. What is the probability that they will have a child with Cystic Fibrosis?

Guided Notes: Complex Genetics

Incomplete Dominance

Sometimes, one allele is not completely ___________ over another allele In this case, the offspring are __________ of both parents

o The ______________ has a unique ________________ because one gene does not completely dominate the other

o Example: _______________ (RR) + ____________ (WW)= _________________(RW) During incomplete dominance, organisms who are

________________________ for a trait have the opportunity to pass ___________________ to the offspring

Therefore, a cross between two __________________organisms have the following:

o 1RR: 2Rr: 1rro 1 Red: 2 Pink: 1 White

Codominance

Sometimes, both alleles are _______________dominanto Therefore, both alleles will be expressed in

_______________ In this case, the offspring display the

__________________________________!o Example: ____________ (WW) + _____________ (BB)= ___________________ (BW)

Case Study: Sickle Cell Anemia

Example: A red carnation is crossed with a white carnation and the resulting offspring are all pink (indicating incomplete dominance). What would be the result of a cross between a pink and a white carnation?

Although we discussed Sickle-Cell Anemia’s recessive inheritance pattern, the disease does display a certain ______________________

o Those homozygous _______________ (aa) have misshapen cellso Those homozygous _______________ (AA) have normal cellso Those ______________(Aa) are unaffected carriers, but can have some misshapen

cells mixed in This unique feature means heterozygous individuals are_____________ to

severe _________________!

Blood Typing

Human blood types include a ____________________ patterno Humans can have type A, B, AB, or O bloodo The alleles involved are two _______________alleles (IA and IB), and one

________________ allele (i)

Genotype Blood Type

Example: A bird with white and blue feathers mates with another white and blue bird (BW). What are the phenotypic ratios of the offspring?

Example: The father is type A homozygous, and the mother is type O. What are the possible blood types of their children?

Sex-Linked Traits

Genes located on the sex chromosomes are called ________________________________ Usually found on the ___________________________ Because of this, _____________ are much more likely to express a trait than females,

because males only have _________ X chromosome!

Let’s take a look at the possible alleles in a recessive sex-linked disease:o Female: __________________________________o Notice that the female must inherit 2 recessive copies to display the trait. It is also

possible for females to be carriers of sex-linked traits.o Male: ____________________________________ o Notice the male does not have a second X to help mask the trait. This means that if he

inherits the recessive copy, he will display the trait!o Because of this, males are much more likely to inherit a sex-linked trait!!!

Common Sex-Linked Traits: o Hemophilia: ____________________________________________________________

______________________________________________________________________

o Color-Blindness: ________________________________________________________

______________________________________________________________________

Example: The father is type A homozygous, and the mother is type O. What are the possible blood types of their children?

Example: Ralph has type B blood and his wife Rachel has type A blood. They are very shocked to hear that their baby has type O blood, and think that a switch might have been made at the hospital. Can this baby be theirs? Explain.

Example: Cross a woman carrier for hemophilia to a hemophiliac man. What percentage of the females could inherit the trait? Males?

Pedigrees

A ________________ is the recorded ancestry of a _________________ Pedigrees allow us to see the _________________ and inheritance patterns through the

___________________ of a family

Pedigrees can give us insight into how traits are passed through families. You can tell a lot through a pedigree. For example:

o The ________________ and ________________ of individualso The ________________ patterno If more males are affected, it is likely sex linkedo If there are no carriers and one of the parents must have it, the disorder is dominanto If carrier parents produce some affected children, the disease must be recessive

Example: Cross a woman carrier for hemophilia to a hemophiliac man. What percentage of the females could inherit the trait? Males?

Example: What type of inheritance pattern is shown below?

What would be the genotype of individual I-1?

Example: What type of inheritance pattern is shown below?

What would the genotypes be of individuals II-1 and III-5?

Example: What type of inheritance pattern is shown below?

What would the genotypes be of individuals II-1 and III-5?