Week 1: Overview of Molecular Genetics

Question 1

Define Mendelian Genetics

Answer 1

Investigates the transmission of traits in successive generations

Question 2

Defne Molecular Genetics

Answer 2

Studies the inheritance, expression, and variation of nucleic acids and proteins

Question 3

Define Evolutionary Genetics

Answer 3

Examines the origins of and genetic relationships among organisms and the evolution of genes and genomes

Question 4

Define Gene

Answer 4

A region of DNA with some biological function

Question 5

Define Allele

Answer 5

One of two or more alternative forms of a gene

Question 6

Define Locus

Answer 6

Specific place on a chromosome occupied by an allele (synonymously coined as gene)

Question 7

Define Genotype

Answer 7

Combination of alleles at one or more loci possessed by an individual organism

Question 8

Define Heterozygote

Answer 8

An individual organism possessing two different alleles at a locus

Question 9

Define Homozygote

Answer 9

An individual organism possessing the same alleles at a locus

Question 10

Define Phenotype or, Alternatively, Trait

Answer 10

The physical form of a biological characteristic resulting from the interaction between a genotype and the environment

Question 11

Changes in DNA sequences (mutations) are linked to ___________

Answer 11

Phenotypic variation

Question 12

Name three things that are required for natural selection to occur

Answer 12

1. variation
2. heritable traits
3. traits that positively influence fitness

Question 13

If certain heritable traits lead to increased success in producing offspring

Answer 13

these traits become more common in the population overtime through inheritance

Question 14

Mendel studies ______ traits, each had only ______ states.

Answer 14

7 traits; dichotomous (two) states

Question 15

Each trait in Mendel’s experiment had ________ and ________ phenotypes that could easily be extinguished

Answer 15

dominant; recessive (no codominance!)

Question 16

Each of Mendel’s experiments started with which strain of pea plants? Why?

Answer 16

pure breeding plants to avoid the appearance of unexpected phenotypes in offspring; inheritance pattern of traits could more accurately be shown

Question 17

In Mendel’s experiment, many offspring could be generated from each cross, which allowed for what?

Answer 17

Phenotypic proportions to accurately be measured

Question 18

Mendel made many ________, repeating the same cross several times. Why?

Answer 18

Replicate crosses to produce hundreds of plants with consistent phenotypes.

Question 19

Mendel also performed __________, in which plants with the same phenotypes are crossed, but the sexes of the donating parents are switched. Why?

Answer 19

Reciprocal crosses to determine if the traits observed are a result of autosomal OR sex chromosomes.

Question 20

State the purpose of test crosses in Mendel’s experiments.

Answer 20

Test crosses were designed to identify the alleles carried by an organism whose genetic makeup is uncertain.

Question 21

Define monohybrid cross

Answer 21

Cross between two individuals that are heterozygotes at a gene that controls a phenotype of interest

Question 22

In pure breeding plants, the parental individuals are ______ for _______ alleles.

Answer 22

homozygous; different.

Question 23

When two pure breeding lines are crossed, what is observed?

Answer 23

100% of the resulting F1 generation exhibits the dominant phenotype

Question 24

When individuals from the F1 generation self fertilize (all heterozygous), the observed phenotypic ratio of the F2 generation is? Genotypic ratio?

Answer 24

3:1
1:2:1 (mendelian ratio)

Question 25

Mendel predicted that all the progeny in his experiment were _______

Answer 25

Heterozygous

Question 26

Among the progeny with the dominant phenotype were plants with the ______ genotype and the _____ genotype.

Answer 26

Homozygous; heterozygous

Question 27

Two scenarios regarding Mendel's test crosses

Answer 27

Scenario 1: if the plant with the dominant phenotype is homozygous, then all the progeny of the test cross will have the dominant phenotype Scenario 2: If the dominant phenotype is due to a heterozygous genotype, then the ratio of the test cross is 1:1

Question 28

State Mendel's Law of Segregation

Answer 28

The alleles of an individual separate during the formation of gametes. Diploid individuals have two versions of each gene (alleles); these versions can be homozygous or heterozygous.

Question 29

How many alleles for a particular biological characteristic does a gamete have?

Answer 29

One single allele for each biological trait!

Question 30

Define dihybrid cross

Answer 30

Cross between parents that are heterozygous at two different genes that control two different phenotypes

Question 31

The double heterozygotes are generated by crossing what?

Answer 31

Two lines that are pure breeding for two different traits

Question 32

Define Mendel's Law of Independent Assortment

Answer 32

The alleles of two or more different genes get sorted into gametes independent of one another. (Note: only true if genes are unlinked)

Question 33

In a dihybrid cross. if the segregation of G and g is independent of the R and r alleles, then _____ of the gametes containing R will also contain G and the other half will carry g.

Answer 33

1/2

Question 34

What are the ratios observed in a dihybrid cross?

Answer 34

Phenotypic: 3:1 Genotypic: 9:3:3:1