12.1 A: Chromosomes & Inheritance

12.1 A: 12.1 A: Chromosomes & Chromosomes &

InheritanceInheritance

Chromosomes…Chromosomes…What are the two types?What are the two types?

• Sex chromosomes and AutosomesSex chromosomes and Autosomes• Sex chromosomes determine?Sex chromosomes determine?• Autosomes code for?Autosomes code for?

• MALE genotype?MALE genotype? FEMALE?FEMALE?

What are these?

Sex Determination—how’s it work?

• Chance of sperm getting X or Y?

• Chance of an egg getting a Y?

• Chance of egg getting X?

• What’s SRY?• Sex-determining Region

Y (gene)..Which means?

SRY = gonad develops as testesSRY = gonad develops as testes

No SRY = ovariesNo SRY = ovaries

Sex Determination

Male or Female?Male or Female?

GAMETES

Brain Break!

Don’t Forget...Family Surveys!

• Due When?

• How many?

• Who at minimum???

2 Types of Mutations

Germ Germ CellCell

Somatic Somatic CellCell

Within those, 2 types too:Chromosome Mutations Gene Mutations

•changes in structure of chromosome •Loss/gain of chromosome

•changes in nucleotides of gene•Loss/gain of nucleotide

•Deletion •Inversion•Translocation•Nondisjunction

•Point•Substitution•Frameshift•Insertion

Deletion Inversion Translocation Nondisjunction

Point Mutation Substitution Frameshift Mutation Insertion Mutation

Chromosomal Mutations

DeletionDeletion

InversionInversion

TranslocationTranslocation

NondisjunctionNondisjunction

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Gene Mutations

Point Point MutationMutation

SubstitutionSubstitution Frameshift Frameshift MutationMutation

Insertion Insertion MutationMutation

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12.1 B: 12.1 B: Chromosomes & Chromosomes &

InheritanceInheritance

Effects of Gene Location

• Morgan’s fruit fly eye-color experiments

• Where is the eye-color gene located?

• XRXR x XRY

• XRXr x XRY

• WHAT’s this called???

Sex-linked Genes and Traits

• Sex-linked trait:• Coded for by allele on sex chromosome (X, Y)

• Is SRY sex-linked?

• Duchenne Muscular Dystrophy, Hemophilia, red/green colorblindness

Duchenne muscular dystrophy

• Gene translation: defective muscle protein

• Lethal, young adults

• 1:3000 males in US

Colorblindness

• Inability to distinguish certain colors

• Red-Green-- • 1:10 males in US;

1:100 females

Hemophilia

• Gene that codes for blood clotting protein

• 1:1000 males

7.3 Gene Linkage and Mapping7.3 Gene Linkage and MappingSo, WHY are more Males Affected?!?!?!?!?So, WHY are more Males Affected?!?!?!?!?

• Female (#23)Genotype:• Male Genotype:• Punnett Square: Normal Dad x Carrier Mom

• Females : carriers (heterozygotes) or AA or aa

• Males only get one X, so if it’s got the bad (recessive) allele, they’re affected

XXYY

Females can Females can carrycarry sex-linked sex-linked genetic disorders but males can’t! genetic disorders but males can’t!

• Males (XY) express all of their X-linked genes.Males (XY) express all of their X-linked genes.• WHY?????WHY?????• SO SO NO MALE HETEROZYGOTES! NO MALE HETEROZYGOTES!

XXYY

If mom’s a carrier of an X-linked recessive disorder and dad’s normal, what’s the probability that they’ll have a normal child?

If dad’s got an X-linked recessive disorder and mom’s normal (not a carrier), what’s the probability that they’ll have a normal child?

Karyotype Activity…

Then wrap up with:Linked GenesMutations

Table 1Table 1Trait

Chromosome for Gene

Location

Dominant Phenotype

Possible Dominant Genotypes

Recessive Phenotype

Recessive Genotype

color of iris 2 not blue EE or Ee blue eewidow's peak

4 Peak PP or Pp no peak pp

cheek dimples

5 Dimples DD or Dd not dimples dd

face freckles

9 Freckles FF or Ff no freckles ff

mid-digital hair

10 Hair HH or Hh no hair hh

Hitchhiker's thumb

17 Straight TT or Tt curved tt

Hallux length (toes)

20long 2nd

toeBB or Bb

long big toe or = to

2nd toebb

ear lobes 21 Free LL or Ll attached lltongue rolling

22 Ability RR or Rr no ability rr

cleft chin 16 Cleft YY or Yy no cleft yy

And this...And this...It is estimated that we all carry between six

and nine lethal recessive genes. Assume you are all carrying (heterozygous)

the recessive disorders in Table 2.Assign your genes to the appropriate

chromosome as done earlier

Table 2 Table 2 Trait

Chromosome for Gene Location

Genotype

skin cancer 1 Cc

cystic fibrosis 7 Qq

albinism 11 Aa

xeroderma pigmentosa

15 Xx

lung cancer 3 Nn

PKU (phenylketonuria)

12 Gg

Muscular Dystrophy X sex chromosome Mm (girls only)

Linked Genes• Same as sex-linked genes?

• Pairs of genes that tend to inherit together

• On fruit flies: eye color and wing length

How the heck do they figure this out?!

• http://my.hrw.com/sh2/sh07_10/student/flash/visual_concepts/60211.htm

p.240 #1,2,6,8

12.2 A: Human GeneticsHuman Genetics

What’s a pedigree diagram?

• Shows inheritance of a trait over several generations

• Horizontal lines• Vertical lines• Circles• Square• Colored/not

colored• Roman #s• Left to right

Tracing genes in Tracing genes in families!!families!!

Phenotypes used to Phenotypes used to inferinfer genotypes!!genotypes!!

Inheritance of TraitsInheritance of TraitsIf autosomal inheritance:

In both sexes equallyRecessive disorders: affected must be hom rec!

PedigreePedigree Male

Female Has trait

No trait

How do you show a carrier????

Inheritance of TraitsInheritance of TraitsIf sex-linked inheritance:

More males than femalesFemales carriers

Check this out! What is Check this out! What is happening from one generation happening from one generation

to the next???to the next???

The gene for this particular genetic trait does not occur on the sex chromosomes; The gene for this particular genetic trait does not occur on the sex chromosomes; it occurs on an autosomal chromosome because both it occurs on an autosomal chromosome because both males and femalesmales and females have the trait. have the trait. This information can be inferred from two facts:This information can be inferred from two facts:

(1) Because the (1) Because the fatherfather has the trait, if the trait were sex-linked (on the father has the trait, if the trait were sex-linked (on the father ’’s X s X chromosome), then chromosome), then all femalesall females would have the trait. However, because some females would have the trait. However, because some females do not have the trait, do not have the trait, it is not a sex-linked trait.it is not a sex-linked trait.

(2) Individual III-7 who (male) didn(2) Individual III-7 who (male) didn’’t inherit the trait from his mom, who has the t inherit the trait from his mom, who has the trait. He received his only X chromosome from his mother.trait. He received his only X chromosome from his mother.

This particular gene is a This particular gene is a dominant genedominant gene because because○ ○ each of the people who have the trait has each of the people who have the trait has only one parentonly one parent who has the trait. who has the trait.○ ○ if only one parent has the trait and the trait is not sex-linked, then the if only one parent has the trait and the trait is not sex-linked, then the

individuals who have the trait must be heterozygous for the gene.individuals who have the trait must be heterozygous for the gene.

• Look at your family history surveysLook at your family history surveys– DRAW on the sheet…DRAW on the sheet…

• Arrange them with Arrange them with – Grandparents = GENERATION IGrandparents = GENERATION I– Parents = GENERATION IIParents = GENERATION II– You, siblings = GENERATION IIIYou, siblings = GENERATION III

• Make connection lines for marriages, etc.Make connection lines for marriages, etc.• HIGHLIGHT ONE TRAIT…asthma, etc.HIGHLIGHT ONE TRAIT…asthma, etc.• Complete the questions!Complete the questions!

Genetic Disorders

• Diseases or disabling traits inherited genetically

• Complex characters:– Environmental factors influence trait also

– Skin color

– Breast cancer, diabetes, heart disease, stroke, schizophrenia

Example of environmental influences?

Smoking, exposure to toxins

In plants: soil acidity

The same flower Grown in different pH soils

Acidic

Basic

What’s the deal?

1.       Trish is Type B and her son, Len, is type AB. What is Ron's blood type?

How do you know?

2.       Is it possible for Janis and John to have a child who is type O?

How can you explain this?

3.       Is it possible for Stacie and Harry to have a child who is type O?

What’s the deal?What’s the deal?

What about Huntington’s disease?What about Huntington’s disease?

DOMINANT allele!Chromosome 4

Memory, emotional issues, muscle spasms, mental illness, death

Not until 30-40 yrs old

12.2 B: Human Genetics

Genetic Testing and Diseases

Genetic Testing: FetalGenetic Testing: FetalAmniocentesis

Fluid, fetal cellsChorionic Villi Sampling

Tissue

Treatment for Genetic DiseasesTreat SYMPTOMS!

PKU:Lack enzyme for phenylalanine tyrosineMental retardationRegulate w/diet: reduce intake of phen.

Cystic Fibrosis:Thick mucus in lungs...

Diabetes:Don’t make enough insulin...

Gene TherapyTomorrow!Replacing the “bad” gene

Human Genome Project

Bioethics

p.248 #1,3,4, 6, 7, 8

p. 250 #5,7,8,10,12,14,15,19,21,22

• http://my.hrw.com/sh2/sh07_10/student/flash/concept_maps/00129.htm