Genetics Intro Flashcards
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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?
2
DNA
Deoxyribonucleic acid
Chromosomes
- 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
Number of chromosomes in humans
46 (23 pairs)
Number of chromosomes in cats
38 (19 pairs)
46 is the ___ number
23 is the ____ number
diploid, haploid
44 (36 for cats) are ____
2 are _______
- autosomes
- sex chromosomes
Between X and Y, which is smaller? Which carries lesser info?
This is reversed in what animals?
Y < X -> Y carries little info
Reversed in birds ( Z and W )
Genes
- 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
Alleles
-different forms of same gene
Homozygous
both allies are the same
heterozygous
alleles are different
Gametes
- 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
Dominant allele
if effect in one allele covers up effect of another allele
Recessie
The allele whose effect was covered up
Alleles have gene will have ____ letter
Dominnat alleles will be ____
Recessive alleles will be _____
Same
Capitalized
Lower-cased
Do what if more than two alleles exist for a gene
Use super-scripts
If we know _____ and ____, we can predict the PHENOTYPE of offspring
- Dominance relationship of alleles
- Genotypes of parents (sire and dam)
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?
- STOP and think.
- Determine what alleles parents can transmit.
- Draw an appropriate Punnet square.
- Place one parent’s alleles on the left side and other’s on top.
- Copy top parent’s alleles down and left parent’s across.
- Determine phenotypes and frequencies.
AA: 1 Dom phenotype
Aa: 2 Dom phenotype
aa: 1 Rec phenotype
Cross involving Sex Chromosomes
- 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!
How many copies of a sex-linked gene will males have?
1
How many copies of a sex-linked gene will females have?
2
Color-blind (sex-linked)
Dominant trait?
Who is often carrier?
- Dom = normal sight
How can we get a color-blind female?
The father must be color blind
Sex linked Recessive traits phenotype is more often in males, Why?
Males only have 1 X chromosome, so if they inherit a recessive allele for sex-linked trait on their x-chromo, they’ll express.
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?
Yes
