Honors Bio - Genetics (Punnett Squares)

Humans have approxomately how many genes?

20,000

Genes are

a sequence of DNA that codes for a protein

How many pairs of homologous chromosomes do you have?

22 pairs of autosomes, and an X-Y pair

Monosomy is

missing a chromosome

Trisomy is

an extra chromosome

Klinefelter is

men with an extra X (XXY)

An autosome is

any cell other than a sex cell

A genotype is

the alleles an organism has

The phenotype is

the physical manifestation of the gene

Monohybrid crosses involve

a cross involving one gene

When you cross two heterozygous parents, what is the genotypic ratio?

1:2:1

When you cross two heterozygous parents, what is the phenotypic ratio?

3:1

Dihybrid crosses are

a punnet with 2 genes

The phenotypic ratio for a double heterozygous dihybrid cross is

9:3:3:1

Mendelian punnets have

one allele that is truly dominant

Incomplete dominance means

the dominant allele isn’t fully expressed if the recessive allele is there (ex. red and white make pink)

Codominance means

both traits are shown (ex. speckled chicken)

A carrier female means the female is

heterozygous

Sex linked punnets need to include

the X and Y for males and females

Who is more likely to be affected by X-related problems?

Males

Men are ___________ for X-genes

hemizygous

For blood types, __ and __ are equally dominant over __

A; B; O

You always cross a test cross with

homozygous recessive

If the phenotypic ratio of a dihybrid test cross is 1:1:1:1, the other one will always be

double heterozygous

Epistasis is when

one gene masks or overrides a completely different gene