Heredity

Question 1

Homologous pairs?

Answer 1

• 2 different copies of the same chromosome in a diploid organism
• 1 from each parent

Question 2

Penetrance?

Answer 2

Proportion of individuals who have the phenotype associated with a specific allele

Question 3

Incomplete dominance?

Answer 3

When one allele is not completely expressed over its paired allele. (R x W= Pink)

Question 4

Codominance

Answer 4

when the heterozygous genotype expresses both alleles. (Ex. red x white = red + white spots).

Question 5

Pleiotropy

Answer 5

when one gene is responsible for many traits
- single gene has multiple phenotypic outcomes

Question 6

Polygenic inheritance

Answer 6

when many genes are responsible for one trait
- multiple genotypes are affecting one phenotype

Question 7

Haploinsufficiency

Answer 7

1 copy of the gene is lost/ nonfunct. and the expression of the remaining copy is not sufficient enough to result in a normal phenotype

Question 8

What organelle contains DNA that only comes from our maternal side?

Answer 8

mitochondria

Question 9

Proto-oncogenes

Answer 9

are genes that can become oncogenes (cancer-causing genes) due to gain-of-function mutations. Cancerous growth occurs as a result
- Normally involved in cell cycle control.
- Follow 1 hit hypothesis

Question 10

Gain-of-function mutations?

Answer 10

Causes too much protein to be made or production of an over-active protein

Question 11

One hit hypothesis?

Answer 11

A gain-of-function mutation in one copy of the gene turns it into an oncogene.

Question 12

Tumor-suppressor genes?

Answer 12

• Genes that become cancerous as a result of loss-of-function mutations
• Normally needed to suppress cancerous growth.
• follow the two hit hypothesis
• Are haplosufficient
• Have null alleles when they become cancer-causing.

Question 13

Two hit hypothesis?

Answer 13

A loss-of-function mutation in both copies of the gene are needed to make it cause cancer.

Question 14

Null alleles?

Answer 14

From mutations that cause the alleles to lack normal function. Tumor-suppressor genes have null alleles when they become cancer-causing.

Question 15

What are the 3 important tumor-suppressing genes?

Answer 15

p53
p21
RB gene

Question 16

p53 is what?

Answer 16

-Tumor-suppressor gene
- Guardian of the cell
- Upregulated to prevent cells from becoming cancerous

Question 17

p21 is what?

Answer 17

• Tumor-suppressor gene
• Inhibits phosphorylation activity in order to decrease rampant cell division.

Question 18

Retinoblastoma gene (RB) is what?

Answer 18

• Tumor-suppressor gene
• Codes for a retinoblastoma protein
• Prevents excessive cell growth during interphase.

Question 19

Nondisjunction is what?
What are the types of this?

Answer 19

• Improper segregation of chromosome pairs during anaphase
• Produces daughter cells with an incorrect # of chromosomes
• Two types: one occurs in Meiosis 1, another occurs in Meiosis 2

Question 20

Single nondisjunction of homologous chromosomes during meiosis I #’s

Answer 20

2n+1, 2n+1, 2n-1, 2n-1

Question 21

Single nondisjunction of homologous chromosomes during meiosis 2 #’s

Answer 21

2n, 2n, 2n+1, 2n-1
- only one side is affected

Question 22

Single nondisjunction of sister chromatids during mitosis #’s

Answer 22

2n+1, 2n-1

Question 23

Aneuploidy

Answer 23

Abnormal # of chromosomes in the daughter cells

Question 24

Trisomy

Answer 24

3 chromosome copies (or 1 extra copy)

Question 25

Monosomy

Answer 25

1 chromosome copies (1 missing copy)

Question 26

Disomy

Answer 26

Refers to a normal diploid cell.

Question 27

Down syndrome

Answer 27

Trisomy of chromosome #21 (each diploid cell has 47 chromosomes total).

Question 28

Turner syndrome

Answer 28

Monosomy of X chromosome in **females** (each diploid cell has 45 chromosomes total).

Question 29

Klinefelter’s syndrome

Answer 29

Trisomy of X in **males** Giving them XXY (each diploid cell has 47 chromosomes total)

Question 30

Trisomy X

Answer 30

Trisomy of X in **females** Giving them XXX (each diploid cell has 47 chromosomes total)

Question 31

True-breeding?

Answer 31

- Organisms are homozygous for all the traits of interest

Question 32

Single allele crosses ratios Homozygous x Homozygous

Answer 32

1/1 AA or 1/1 Aa or 1/1 aa

Question 33

Single allele crosses ratios Homozygous x Heterozygous

Answer 33

1/2 AA OR 1/2 aa AND 1/2 Aa ex. 1/2 aa and 1/2 Aa

Question 34

Single allele crosses ratios Heterozygous x Heterozygous

Answer 34

1/4 AA, 1/2 Aa, 1/4 aa

Question 35

How do you understand/figure out multiple allele crosses?

Answer 35

You multiply the single allele cross ratios - MULTIPLY the denominators!

Question 36

Pedigree Charts What is the symbol for females?

Answer 36

Circles

Question 37

Pedigree Charts What is the symbol for males?

Answer 37

Squares

Question 38

Pedigree Charts What is the symbol for affected individuals?

Answer 38

A shaded circle/square is affected, not affected is not shaded

Question 39

Where is genetic material at points exchanged during crossing over?

Answer 39

Chiasmas

Question 40

What does autosomal dominant mean?

Answer 40

Non-sex gene, only 1 mutant gene required to cause disorder **equal frequency in both sexes!**

Question 41

What does autosomal recessive mean?

Answer 41

Non-sex gene, 2 mutant genes required to cause disorder **skipping of generations!**

Question 42

Linked genes

Answer 42

Different genes in close physical proximity on the same chromosome

Question 43

Epistasis

Answer 43

Occurs when one gene affects the expression of a second gene

Question 44

_____ changes can cause _____ twins to have different susceptibilities to the same disease.

Answer 44

Epigenetic, monozygotic

Question 45

Recombination frequencies of _______ mean that the two genes are _______.

Answer 45

less than 50%, linked

Question 46

Haplotype

Answer 46

Group of genes that are usually inherited together because they are located in close proximity to each other

Question 47

What are the three types of sex-linked traits

Answer 47

X-linked dominant X-linked recessive Y-linked

Question 48

X-linked dominant

Answer 48

sex gene, only 1 mutant gene required **dad affected, ALL daughters are affected** Dominant inheritance on the X chromosome. Any offspring (male or female) that receive the affected allele will end up with the disorder.

Question 49

X-linked recessive

Answer 49

sex gene, 2 mutant genes required Females: 2 affected alleles are needed to cause the disorder Males: only 1 affected allele is needed to cause the disorder **more affected males!** Recessive inheritance on the X chromosome

Question 50

Y-linked

Answer 50

sex gene ALWAYS expressed, dominant or recessive because males only have one Y chromosome. ONLY be passed from father to son (very rare)

Question 51

How many X chromosomes do women have?

Answer 51

2 X chromosomes

Question 52

Examples of X-linked recessive conditions.

Answer 52

Hemophilia and Color-blindness

Question 53

Genomic imprinting

Answer 53

Genes that are expressed depending on parental origin

Question 54

X-inactivation

Answer 54

Process by which one of a female’s X chromosomes is inactivated, forming a Barr body and preventing excess transcription *Female carrier can become affected*

Question 55

Epigenetics

Answer 55

Does not involve modifying the genetic code, but instead the regulation of when genes are expressed.

Question 56

Examples of epigenetics

Answer 56

DNA methylation Histone acetylation Histone de-acetylation Histone methylation

Question 57

DNA methylation

Answer 57

Decreases gene expression by the suppression of genes. This is done through the addition of methyl groups, recruiting methyl-binding proteins (MBDs) and preventing transcription factors from binding.

Question 58

Histone acetylation

Answer 58

causes gene *activation* and formation of euchromatin (easily accessible DNA).

Question 59

Histone de-acetylation

Answer 59

causes gene *suppression* (think ‘de-activation’) and formation of heterochromatin (hard to access DNA).

Question 60

Histone methylation

Answer 60

can upregulate/downregulate gene expression

Question 61

Euchromatin

Answer 61

easily accessible DNA

Question 62

Heterochromatin

Answer 62

hard to access DNA

Question 63

Allele

Answer 63

one variation of a gene