Genetics Intro

Question 1

In cats, there is a gene that controls hair color. The allele for grey hair is recessive to the allele for black hair. If a heterozygous female mates with a grey male and then has 8 kittens, how many o the kittens would be expected to be grey?

Answer 1

2

Question 2

DNA

Answer 2

Deoxyribonucleic acid

Question 3

Chromosomes

Answer 3

• in cell nucleus
• long DNA chains
• carry info for lots of traits
• individual bits of info = “genes”
• Number per cell varies between species
  Exist in pairs in somatic (body) cells

Question 4

Number of chromosomes in humans

Answer 4

46 (23 pairs)

Question 5

Number of chromosomes in cats

Answer 5

38 (19 pairs)

Question 6

46 is the ___ number
23 is the ____ number

Answer 6

diploid, haploid

Question 7

44 (36 for cats) are ____
2 are _______

Answer 7

• autosomes
• sex chromosomes

Question 8

Between X and Y, which is smaller? Which carries lesser info?

This is reversed in what animals?

Answer 8

Y < X -> Y carries little info

Reversed in birds ( Z and W )

Question 9

Genes

Answer 9

• Small chromosomes parts
• control one specific trait/part of trait
• may be in different forms on pair of chromosomes
• different forms (of same gene) are called “alleles”
  -> homozygous, heterozygous

Question 10

Alleles

Answer 10

-different forms of same gene

Question 11

Homozygous

Answer 11

both allies are the same

Question 12

heterozygous

Answer 12

alleles are different

Question 13

Gametes

Answer 13

• haploid
• only contain 1 copy of each chromosome
• random 50/50 chance of which one it contains
• can then only contain an X or a Y chromosome

Question 14

Dominant allele

Answer 14

if effect in one allele covers up effect of another allele

Question 15

Recessie

Answer 15

The allele whose effect was covered up

Question 16

Alleles have gene will have ____ letter

Dominnat alleles will be ____

Recessive alleles will be _____

Answer 16

Same

Capitalized

Lower-cased

Question 17

Do what if more than two alleles exist for a gene

Answer 17

Use super-scripts

Question 18

If we know _____ and ____, we can predict the PHENOTYPE of offspring

Answer 18

1. Dominance relationship of alleles
2. Genotypes of parents (sire and dam)

Question 19

There is a trait which is controlled by gene “A”. -> A, a

What should we expect the offspring to be life if we cross two heterozugous parents?

Answer 19

1. STOP and think.
2. Determine what alleles parents can transmit.
3. Draw an appropriate Punnet square.
4. Place one parent’s alleles on the left side and other’s on top.
5. Copy top parent’s alleles down and left parent’s across.
6. Determine phenotypes and frequencies.

AA: 1 Dom phenotype
Aa: 2 Dom phenotype
aa: 1 Rec phenotype

Question 20

Cross involving Sex Chromosomes

Answer 20

• same principles are used
• RM: either X or Y will be passed on by male
• RM: one X or the other X will be passed from female
• Y chromosomes are small and often don’t carry an allele
• SO, males will only have 1 copy of sex-linked gene
• Females have 2!

Question 21

How many copies of a sex-linked gene will males have?

Answer 21

1

Question 22

How many copies of a sex-linked gene will females have?

Answer 22

2

Question 23

Color-blind (sex-linked)

Dominant trait?
Who is often carrier?

Answer 23

• Dom = normal sight

Question 24

How can we get a color-blind female?

Answer 24

The father must be color blind

Question 25

Sex linked Recessive traits phenotype is more often in males, Why?

Answer 25

Males only have 1 X chromosome, so if they inherit a recessive allele for sex-linked trait on their x-chromo, they’ll express.

Question 26

The orange / non-orange gene is sex-linked in cats.
It is co-dominant. The O allele gives orange color
and the o allele gives non-orange color.
If an orange queen mates with a non-orange tom, can
we determine the sex of the kittens by their color?

Answer 26

Yes