Bio: Genetics

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When doing a punnett square for 2 parents and their child's possibility of a trait, how many punnett squares do you do?

2, one for each possibility
When doing a punnett square for genes or genotypes, what is different?
- You use X's and Y's with the capital and lower case letters.
- Examples:
- X^BX^b
- X^BY
- *note: Y will never get a letter with it.
Why do sex-linked traits typically affect more men than women?

Males have 1 X chromosome, which is where the sex-linked trait is located, and the Y chromosome is blank.
When does independent assortment occur?

Metaphase I of meiosis
During Anaphase II of meiosis, what separates?

SISTER chromatids
What causes nondisjunction?

when a mitotic spindle breaks during cytokenesis.
Phenotype

observable or physical trait
Genotype

genetic code that explains phenotype
Gene

unduplicated segment of a chromosome that codes for a trait
Allele

alternate form of a trait or gene
Homozygous
- 2 copies of the same allele
- Examples:
- YY or yy
Heterozygous
- 1 copy of each allele
- Example:
- Yy
Pleiotropy

one gene affects many phenotypes
Polygenic inheritance

many genes affect 1 phenotype
External thing that affects gene expression

Environment
Chance of having a boy or girl?

50% for both
Which is physically bigger: X or Y chromosome?

X
X chromosome has _____ base pairs
Y chromosome has _____ base pairs
- X= 153 million
- Y= 50 million
Colorblindness is ______ and on the ___ chromosome.

recessive; X