Inheritance and DNA

Question 1

Gene

Answer 1

a fundamental unit of heredity that is passed from parent to offspring. Genes are made up of DNA and are located on chromosomes in the nucleus of cells. They contain information for making proteins, which are responsible for specific traits or functions in the body

Question 2

Allele

Answer 2

alternate forms of a gene that code for different proteins

Question 3

Wild type

Answer 3

allele present in most of the population

Question 4

Mutation

Answer 4

stable, inherited change in genetic material, where new alleles arise

Question 5

True breeding

Answer 5

a term used in genetics and selective animal breeding to describe organisms or animals that pass on the same traits to their offspring

Question 6

Phenotype vs genotype

Answer 6

• Phenotype: physical appearance of an organism
• Genotype: genetic constitution of an organism

Question 7

Dominant vs recessive

Answer 7

• Dominant alleles: are expressed; exert their effects whenever they’re present
• Recessive alleles: effect is masked if dominant allele also present; may be mutated and no longer expressed, or encode non‐functional proteins

Question 8

Homozygous vs heterozygous

Answer 8

• Homozygous: two alleles are the same
• Heterozygous: two different alleles; one may be dominant and the other recessive

Question 9

P vs. F1 vs. F2

Answer 9

The parent or P generation refers to the individuals being crossed; the offspring are the filial or F generation. F₁ or the first filial represents the children of the parents; F₂ represents children of the F₁ or grandchildren of the parents

Question 10

Gregor Mendel’s 1st law

Answer 10

Law of segregation: the two copies of a gene separate during gamete formation; each gamete receives only one copy

Question 11

Mendel’s 2nd law

Answer 11

Law of independent assortment: copies of different genes assort independently

Question 12

Who do offspring inherit alleles from

Answer 12

Offspring inherit alleles from both of their parents; each parent contributes one allele for every gene, meaning the offspring receives a pair of alleles for each trait, one from the mother and one from the father

Question 13

Multiplication rule

Answer 13

probability of two independent events
happening together –multiply by probabilities of the individual events
– Tossing two coins: probability that both will come up heads = ½ x ½ = 1/4

Question 14

Addition rule

Answer 14

the probability of an event that can occur in two different ways is the sum of the individual probabilities
– In F2, there are two ways to get Rr, thus ¼ + ¼ = ½

Question 15

Codominant vs incomplete dominance

Answer 15

Codominance: more than one allele
encodes a functional protein
Incomplete dominance: alleles are neither dominant nor recessive – heterozygotes have an intermediate phenotype

Question 16

Locus

Answer 16

specific position on a chromosome

Question 17

Linked genes

Answer 17

genes that are located close together on a chromosome and are often inherited together

Question 18

Pleiotropic vs. epistatic

Answer 18

Pleiotropic: one allele has multiple phenotypic effects
Epistasis: phenotypic expression of one gene influenced by another gene

Question 19

What environmental conditions can affect expression of genotype

Answer 19

Light, temperature, nutrition, etc., can affect expression of the genotype

Question 20

Coat patterns of Siamese cats and rabbits

Answer 20

Point restriction coat patterns in Siamese cats and rabbits
- Enzyme that produces dark fur inactive at higher temps.
- Nose, ears, etc., are cooler, thus darker in color

Question 21

How can prokaryotes exchange genes

Answer 21

horizontal gene transfer” which primarily occurs through three mechanisms: conjugation (direct cell-to-cell contact via a pilus), transformation (taking up free DNA from the environment), and transduction (transfer of DNA by a virus)

Question 22

Plasmid and what genes it contain

Answer 22

small, circular DNA molecules that can contain a variety of genes, including those that confer antibiotic resistance, virulence, and the ability to grow in adverse conditions

Question 23

Rosalind Franklin

Answer 23

Rosalind Franklin prepared crystallography from DNA samples
- Her images suggested a double helix with 10 nucleotides/turn
- 2 nm diameter suggested the sugar‐phosphate backbone must
be on outside

Question 24

Crick and Watson

Answer 24

used model building, plus physical and
chemical evidence, to solve DNA structure
– Published their results in 1953

Question 25

Structure of DNA

Answer 25

Biochemists knew DNA is a polymer of nucleotides
– Each nucleotide consists of deoxyribose, a phosphate group, and a nitrogen‐containing base

Question 26

Four different nucleotides differing only in the bases

Answer 26

Purines: adenine (A) and guanine (G)
Pyrimidines: cytosine (C) and thymine (T), holds DNA together

Question 27

DNA vs. RNA nucleotides

Answer 27

DNA: Pu. A -> Py. T, Pu. G -> Py. C
RNA: Pu. A -> U (Uracil), Pu. G -> Py. C

Question 28

DNA structure setup

Answer 28

• Bases are on the inside of each strand
• Sugar‐phosphate groups on outside
• Chains are antiparallel: run in opposite direction
• DNA can be found in the nucleus of the cell

Question 29

Chargaff’s rule

Answer 29

The amount of adenine is always equal to the amount of thymine found in a sample. The amount of cytosine is always equal to the amount of guanine found in a sample

Question 30

DNA strands held together by

Answer 30

• hydrogen bonds between complementary base pairs
• Van der Waals forces between adjacent bases on same strand

Question 31

DNA replication

Answer 31

the process by which cells create two identical copies of DNA from a single original DNA molecule

Question 32

Semi conservative

Answer 32

each parent strand is a template; new molecules have one old and one new strand

Question 33

2 step DNA replication

Answer 33

• Double helix unwound, making two template strands
• New nucleotides form complementary base pairs with the template DNA strand and are linked by phosphodiester bonds

Question 34

origin of replication and replication fork

Answer 34

• Origin of replication (ori): specific region of DNA that indicates the starting point of replication
• In E. coli, DNA is unwound, and replication proceeds in both directions, forming two replication forks

Question 35

Leading vs. lagging strand and Okazaki fragments

Answer 35

• Leading strand: grows at the 3’ end as the fork opens
• Lagging strand: the exposed 3’ end gets farther from the fork, and an unreplicated gap form
• Okazaki fragments: small, discontinuous stretches of new DNA

Question 36

3 repair mechanisms

Answer 36

• Proofreading: DNA polymerase recognizes mismatched pairs
  and removes incorrectly paired bases
• Mismatch repair: newly replicated DNA is scanned for mistakes by other proteins, and mismatches can be corrected
• Excision repair: enzymes scan DNA for damaged bases – they’re excised, and DNA polymerase I adds the correct ones

Question 37

PCR

Answer 37

Polymerase chain reaction (PCR): an automated process that makes multiple copies of short DNA sequences for genetic
manipulation and research