Flashcard Set

AP Biology: Genetics and Heredity

14 cards

Meiosis, Mendelian and non-Mendelian inheritance, and chromosomal genetics for the AP Biology exam.

1
Term
How does the random orientation of homologous chromosomes along the metaphase plate in meiosis I contribute to genetic variation?
Definition
It leads to independent assortment, allowing maternal and paternal chromosomes to separate randomly into gametes, creating 2^n possible chromosome combinations.
2
Term
During prophase I of meiosis, homologous chromosomes pair up and exchange genetic material in a process called ___.
Definition
crossing over
3
Term
Which physical event in meiosis explains Mendel's Law of Segregation, where alleles for a single gene separate into different gametes?
Definition
The separation of homologous chromosomes during anaphase I.
4
Term
What physical event in meiosis forms the biological basis of Mendel's Law of Independent Assortment?
Definition
The random alignment of different homologous chromosome pairs along the metaphase plate during metaphase I.
5
Term
In a cross of AaBbCc x AaBbCc, what is the probability of producing an offspring with the genotype AAbbCc?
Definition
1/32 (Reasoning: P(AA) = 1/4, P(bb) = 1/4, and P(Cc) = 1/2. Using the rule of multiplication: 1/4 * 1/4 * 1/2 = 1/32).
6
Term
Why are biological males (XY) affected by X-linked recessive disorders much more frequently than biological females (XX)?
Definition
Males are hemizygous for the X chromosome, meaning they only have one allele; if that single allele is recessive, they will express the disorder.
7
Term
What is the key phenotypic distinction between codominance and incomplete dominance in a heterozygote?
Definition
In codominance, both alleles are fully and distinctly expressed (e.g., AB blood type); in incomplete dominance, the phenotype is an intermediate blend (e.g., pink flowers from red and white parents).
8
Term
Two genes on the same chromosome have a recombination frequency of 18%. What does this tell us about their distance on a chromosome map?
Definition
They are linked and situated 18 map units (or centimorgans) apart.
9
Term
Why can the recombination frequency between two genes on the same chromosome never exceed 50%?
Definition
A recombination frequency of 50% represents independent assortment, which occurs when genes are so far apart that crossing over is guaranteed to occur randomly between them.
10
Term
An inherited trait is passed down from an affected mother to all of her offspring, but affected fathers never pass it on. What is the inheritance pattern?
Definition
Mitochondrial (or maternal) inheritance, because mitochondria are inherited exclusively from the maternal egg cell.
11
Term
If your calculated chi-square value is less than the critical value at p = 0.05, do you reject or fail to reject the null hypothesis, and what does this mean for your genetic model?
Definition
Fail to reject the null hypothesis. Any differences between observed and expected offspring ratios are due to random chance, supporting your genetic model.
12
Term
What is epistasis?
Definition
A gene interaction where the allele of one gene masks or modifies the phenotypic expression of a second, completely different gene.
13
Term
What is phenotypic plasticity?
Definition
The ability of a single genotype to produce different phenotypes in response to varying environmental conditions (e.g., hydrangea color changes due to soil pH).
14
Term
If nondisjunction occurs during meiosis I, what percentage of the four resulting gametes will have an abnormal chromosome number?
Definition
100% (All four gametes are affected: two will have n+1 chromosomes, and two will have n-1 chromosomes).