Introduction to genetics flashcards

Question 1

Mendel’s law of segregation

Answer 1

Every individual has a pair of alleles for each trait and each parent randomly passes one allele to their offspring

Question 2

Mendel’s law of independent assortment

Answer 2

Separate genes for separate traits are passed down independently from parent to offspring Unless linked

Question 3

Point mutations

Answer 3

In coding or noncoding regions. If in noncoding regions can still lead to disease by affecting splicing, promoter regions, etc

Question 4

Missense mutations

Answer 4

Alter sequence of an encoding protein

Question 5

Nonsense mutations

Answer 5

Amino acid is changed to a stop codon

Question 6

Deletions or insertions

Answer 6

If 3 base pairs involved protein still made but altered. If not a multiple of 3 frameshift mutation occurs which usually truncates protein

Question 7

Trinucleotide expansion

Answer 7

Amplification of 3 nucleotides-areas that have the same AA sequence over and over again. Dynamic process (tend to amplify during gametogenesis)

Question 8

Factors (in genetics)

Answer 8

Another name for genes

Question 9

Mendelian disorders

Answer 9

Due to mutation in single gene, follow 3 common patterns of inheritence (autosomal dominant, autosomal recessive, X-linked)

Question 10

Autosomal dominant

Answer 10

Manifest in heterozygous state, typically have an affected parent. 50% chance of inheriting disease with one affected parent. Both males and females equally affected and disease seen in each generation.

Question 11

Incomplete penetrance

Answer 11

Inherit a mutant gene but appear normal

Question 12

Variable expressivity

Answer 12

Trait is seen in all patients carrying mutant gene, but different phenotypes result

Question 13

Autosomal recessive

Answer 13

Both alleles must be mutated. 25% chance of having the disease and 50% chance of being a carrier with 2 carrier parents. Trait does not usually affect parent, but siblings may be affected. If trait very rare might be due to consanguinous coupling.

Question 14

X-linked

Answer 14

Mutation in X chromosome. Men are hemizygous. Men do not transmit to sons but transmit to all daughters. Heterozygous woman does not express full phenotype because of the normal X copy due to X-inactivation. If “dominant” more women than men affected. If “recessive” more men affected than women. Really no such thing as dominant/recessive X-linked. If mutation in secreted protein cells can share yielding recessive behavior. If in intracellular protein (structural, regulatory) cannot share and get domanant behavior with less severe disease women.

Question 15

Proband

Answer 15

Individual who is identified first (usually the patient)

Question 16

Consanguinous marriage

Answer 16

Marriage between 2 related individuals

Question 17

Hemizygous

Answer 17

One member of a chromosome pair (only one X in males)

Question 18

X-inactivation

Answer 18

One chromosome randomly inactivated in cells of women

Question 19

Pedigree rules

Answer 19

Box: male Circle: female Shaded: affected Slash: deceased Half-shaded: heterozygotes for autosomal recessive Dot: carrier for X-linked recessive

Question 20

Huntington’s disease

Answer 20

Gene on chromosome 4. Autosomal dominant disease caused by trinucleotide expansion >40 repeats (every time disease passed down number of repeats changes, usually getting larger and more severe). Dementia, cholera (jerky movements).

Question 21

Niemann-Pick disease

Answer 21

Autosomal recessive metabolic disorder caused by mutation in NPC gene. Onset in childhood. Clumsy walking, slurred speech, impaired memory, seizures.

Question 22

Fragile X syndrome

Answer 22

Trinucleotide expansion causing autism, intellectual disability, seizures.

Question 23

Co-dominant

Answer 23

Two different alleles expressed and influence trait, each making slightly different protein.

Question 24

Mitochondrial inheritance

Answer 24

Inherited through maternal line. Trait appears in every generation. Rare because mtDNA changes at slow rate. Associated diseases usually affect neuromuscular system.

Question 25

Mitochondrial DNA (mtDNA)

Answer 25

Contains 37 genes and all essential for function. 13 genes are instructions for making enzymes for oxidative phosphorylation. Remaining genes for making tRNA, rRNA. Sperm carries mitochondria in tail which falls off during fertilization.

Question 26

Heteroplasmy

Answer 26

Presence of more than one mtDNA variant (normal and mutated). Must have enough mutated copies to show disease called threshold effect. Higher ratio of mutated copies means more severe disease. Expression is highly variable.

Question 27

Epigenetics

Answer 27

Study of changes in gene expression or cellular phenotype caused by mechanisms other than changes in underlying DNA (meaning chemical reactions turning genes on and off). Some shown to be heritable.

Question 28

Hardy-Weinberg equation

Answer 28

p2+2pq+q2=1 Model for calculating genotype frequencies from allele frequencies for random-mating population in equilibrium

Question 29

Hardy-Weinberg 6 assumptions

Answer 29

1. Large population 2. Random mating 3. Allele frequencies same in men and women 4. No mutation 5. No selection 6. No migration

Question 30

Imprinting

Answer 30

Occurs in the ovum or sperm before fertilization. Both copies of genes turned on, but some genes selectively inactivated. Maternal imprinting silences of maternal allele and paternal imprinting silences paternal allele.

Question 31

Prader-Willi disease

Answer 31

Only paternal copy activated. Loss of function genes on chromosome 15. Hyperphagia (overeating), obesity, intellectual disability.

Question 32

Angelman disease

Answer 32

Only maternal copy active. Loss of function genes on chromosome 15. Happy, excitable, intellectual disability, speech/movement issues, seizures.