Question 1

What is meiosis?

Accepted Answer

A process where a single cell divides twice to produce four cells containing half the original amount of genetic information

(these four cells are sex cells)

Question 2

What are homologous chromosomes?

Accepted Answer

Two pieces of DNA that carry the same genes, one from each parent

(humans have 23 homologous chromosomes, which creates 46 in total)

Question 3

What are gametes?

Accepted Answer

Haploid sex cells produced during meiosis

Unite with another gamete of the opposite sex to form a zygote

Question 4

What is spermatogenesis?

Accepted Answer

Process of gamete formation in males, leading to the production of four haploid sperm from each meiotic cycle

Question 5

What is oogenesis?

Accepted Answer

Process of gamete formation in females, leading to the production of a single ovum/egg per meiotic cycle

(more complicated than spermatogenesis)

Question 6

What are polar bodies?

Accepted Answer

Small cells in oogenesis that simply receive half the genetic information and are cast away

(the remaining cell receives most of the cytoplasm and may become the ovum)

Question 7

How is oogenesis different from spermatogenesis?

Accepted Answer

After meiosis I, one cell recieves half the genetic information and the majority of the cytoplasm (the polar body is discarded)

During meiosis II, the remaining cell divides again to become the ovum (forms another polar body which is also discarded)

Question 8

What happens to the excess cytoplasm in oogenesis?

Accepted Answer

Used for proper growth of the embryo after fertilization

Question 9

Why is it important that sperms and eggs are haploid (and not diploid)?

Accepted Answer

If they were diploid, the offspring would contain twice as many chromosomes as the original parents

(meiosis solves this by producing haploid gametes)

Question 10

What is the difference between how chromosomes are treated in meiosis and mitosis?

Accepted Answer

In meiosis during prophase I homologous pairs join together, so during metaphase I, they align along the metaphase plate in pairs

In mitosis chromosomes are alone, so during metaphase, they align along the metaphase plate alone

Question 11

What is crossover (crossing over)?

Accepted Answer

A process in meiosis where homologous chromosomes swap pieces

Question 12

Why is crossover important?

Accepted Answer

It increases genetic diversity and allows offspring to differ from their parents

Question 13

What is an autosomal chromosome (autosome)?

Accepted Answer

Any numbered chromosome that is not a sex chromosome

Question 14

What is a wild-type phenotype?

Accepted Answer

Typical/most-common phenotype for a trait in a given species

(opposite of a mutant phenotype)

Question 15

What is a mutant phenotype?

Accepted Answer

Traits that are different from the normal for a given species

(opposite of wild-type)

Question 16

What are sex-linked traits?

Accepted Answer

Genetic characteristics determined by genes on sex chromosomes

(often affect one gender much more than the other; e.g., DMD, hemophilia, red-green color blindness)

Question 17

Why are do some genetic disorders affect one gender more than the other?

Accepted Answer

Some genetic disorders have a recessive allele on the X chromosome

Women have two X chromosomes, while men only have one, so women have to get two copies of the gene to have the disorder

Question 18

What is Duchenne muscular dystrophy (DND)?

Accepted Answer

A sex-linked disorder caused by the absence of an essential muscle protein, causing loss of strength and coordination

(much more common in men)

Question 19

What is hemophilia?

Accepted Answer

A sex-linked disorder caused by the absence of a protein vital to clotting blood

(much more common in men)

Question 20

What is red-green color blindness?

Accepted Answer

A sex-linked disorder that causes the inability to distinguish red and green

(more common in men)

Question 21

What is X inactivation?

Accepted Answer

A process females undergo during embryonic development, where cells randomly inactivate one of the two X chromosomes

(the inactivated X chromosome is known as the Barr body)

Question 22

What is Barr body?

Accepted Answer

The inactivated X chromosome in all female cells, as a result of X inactivation

Question 23

What are holandric traits?

Accepted Answer

Traits inherited via the Y chromosome, only affecting males

(hypertrichosis pinnae, which causes excessive hair in the ear, only affects males)

Question 24

What are linked genes?

Accepted Answer

Genes likely to be inherited together because they lie physically close on the same chromosome

(do not follow Mendel's law of independent assortment)

Question 25

Why are linked genes less susceptible to being mixed up by crossover?

Accepted Answer

Linked genes are physically close to each other, so crossover is less likely to affect them

Question 26

What is a linkage map?

Accepted Answer

Tables to visualize the order and relative frequency of genes on a chromosome

(created by finding recombination frequencies for gene pairs)

Question 27

What is a centimorgan (map unit)?

Accepted Answer

A unit for measuring genetic linkage

(one centimorgan is equal to 1% crossover frequency)

Question 28

What are pedigrees?

Accepted Answer

Family trees used to describe genetic relationships within a family

Question 29

What are Punnett squares?

Accepted Answer

A square diagram to predict the genotypes of a breeding experiment

Question 30

What are haploid (n) organisms?

Accepted Answer

An organism that only has one copy of each type of chromosome

Question 31

What are diploid (2n) organisms?

Accepted Answer

An organism that has two copies of each type of chromosome

Question 32

What is the meaning of n and 2n in heredity?

Accepted Answer

n represents the number of sets of chromosomes

(n = one set of chromosome (haploid), 2n = two sets of chromosomes (diploid), 4n = four complete sets of chromosomes)

Question 33

What are the limitations of Mendel's work?

Accepted Answer

It cannot account for many patterns of inheritance, such as...

sex-linked traits, incomplete dominance, and codominance

Question 34

What is non-nuclear inheritance?

Accepted Answer

Offspring getting DNA only from the male or female parent

(humans get mitochondrial DNA from the only the mother and never the father)

Question 35

What is intermediate inheritance?

Accepted Answer

When an individual with a heterozygous trait displays characteristics that are different from both parents

(their phenotype is a "mixture" of both of the parents' genes; two types: incomplete dominance and codominance)

Question 36

What is incomplete dominance (blending inheritance)?

Accepted Answer

When a dominant allele does not completely mask the effects of a recessive allele

(crossing a red snapdragon with a white snapdragon will result in a pink snapdragon)

Question 37

What is familial hypercholesterolemia (FH)?

Accepted Answer

A recessive disorder that causes very high cholesterol levels, leading to heart attacks in children as young as 2

(example of incomplete dominance because having a single recessive allele (Hh) will cause higher chol. levels than having two dominant alleles (HH), but having two recessive alleles (hh) will fully cause the disorder)

Question 38

What is codominance?

Accepted Answer

When both a dominant and recessive allele fully express themselves in a heterozygous organism

(individuals with M blood have M glycoproteins on blood cells, those with N blood have N glycoproteins, and those with MN blood have both)

Question 39

What are polygenic traits?

Accepted Answer

Traits affected by more than one gene

(eye color and skin color)

Question 40

What is epistasis?

Accepted Answer

When the expression of one gene affects the expression of another

Question 41

What is pleiotropy?

Accepted Answer

When a single gene has multiple effects on an organism

Question 42

What is an allele?

Accepted Answer

A variant of a gene for a particular trait

Question 43

What are F₁ and F₂?

Accepted Answer

The first and second filial generations

The initial cross between two distinct plants, and the cross of sister seedlings from the first cross

Question 44

What is a genotype?

Accepted Answer

All the genes that make up an individual

(genotype = genes)

Question 45

What does it mean to be heterozygous for a gene?

Accepted Answer

The two alleles that make up that gene are different

(having one allele for red hair and one allele for brown hair)

Question 46

What does it mean to be homozygous for a gene?

Accepted Answer

The two alleles that make up that gene are the same

(having two alleles for red hair, or having two alleles for brown hair)

Question 47

What is a karyotype?

Accepted Answer

A technique for producing a chart of an individual's chromosomes

Question 48

What is nondisjunction?

Accepted Answer

Improper separation of chromosomes during meiosis, causing an abnormal number of chromosomes in offspring

(causes variety of disorders, such as Down, Turner, and Klinefelter syndromes)

Question 49

What is P₁?

Accepted Answer

The parent generation in a cross

Question 50

What is a phenotype?

Accepted Answer

Physical characteristics on an individual, resulting from how its genotype interacts with the environment

(physical characteristics = phenotype)

Question 51

What is a character in genetics?

Accepted Answer

A genetically inherited characteristic

Question 52

What was the blending hypothesis?

Accepted Answer

An incorrect hypothesis that stated offspring are a blend of their parents' genes

A blue flower and a yellow flower would make a green flower

(popular before Mendel's work in the 1850s; proven false)

Question 53

What is a monohybrid cross?

Accepted Answer

A cross between two organisms on a single trait

Question 54

What is a dihybrid cross?

Accepted Answer

A cross between two organisms on two different traits at once

Question 55

What is the law of segregation (Mendel's First Law)?

Accepted Answer

Every organism has a pair of alleles for each trait

These alleles segregate/separate when gametes for formed

Question 56

What is the law of independent assortment (Mendel's Second Law)?

Accepted Answer

The inheritance of one trait does not affect the inheritance of another

(technically: pairs of alleles are distributed independently when gametes are formed)

Question 57

What is the law of dominance?

Accepted Answer

When an organism is heterozygous for a trait, only the dominant allele will produce a phenotype

Question 58

What is a test cross?

Accepted Answer

A test created by Mendel to determine an organism's genotype

Geneticists breed an organism with an unknown genotype, with an organism that is homozygous recessive for a given trait, and analyze the offspring

Question 59

What is Tay-Sachs disease?

Accepted Answer

A fatal genetic disorder that causes the destruction of nerve cells in the brain and spinal cord

(inability to break down a particular type of lipid in the brain; recessive)

Question 60

What is cystic fibrosis (CF)?

Accepted Answer

A genetic disorder that causes thick mucus to accumulate in the lungs and digestive tract

(gene is located on chromosome 7; kills children at a young age if untreated)

Question 61

What is sickle cell anemia?

Accepted Answer

A recessive genetic disorder that causes hemoglobin to deform to a "sickle" shape, making it less efficient at carrying oxygen

(with only one copy, you get increased resistance to malaria, but with both copies, you get sickle cell anemia)

Question 62

What is phenylketonuria (PKU)?

Accepted Answer

A recessive genetic disorder that may lead to an intellectual disability if untreated

(causes inability to successfully digest an amino acid called phenylalanine)

Question 63

What is Huntington disease?

Accepted Answer

A fatal, dominant genetic disorder that causes the breakdown of the nervous system

(dominant, not recessive!; only appears when a person is in their 30s/40s)

Question 64

Why are lethal recessive alleles more common than lethal dominant alleles?

Accepted Answer

Individuals with lethal recessive alleles can live and reproduce perfectly fine, spreading the allele to their children

Individuals with lethal dominant alleles will most likely die before spreading the allele to their children

Unit 5: Heredity, AP Biology Flashcards