BIO4: Medelian Genetics, Meiosis, and Genetic Diversity

Question 1

Gene

Answer 1

Sequence of DNA that encodes for a certain protein/function in cell

Question 2

Allele

Answer 2

Different versions of a gene (but located on the same locus)

Question 3

Locus

Answer 3

Certain position on a chromosome representing the location of a gene

Question 4

Diploid

Answer 4

Diploid organisms have 2 sets of chromosomes (one homologous chromosome from each parent which have the same set of genes but may have different alleles/heterozygous)

Question 5

Haploid

Answer 5

Haploid organisms have 1 set of chromosomes which determines gene expression (no dominant/recessive)

Question 6

Polygenic trait

Answer 6

A trait that is controlled by 2 or more different genes (e.g. height)

Question 7

Complete dominance

Answer 7

AA and Aa both show dominant phenotype

Question 8

Wild type

Answer 8

The most common form of a trait (may be recessive allele); other form is usually called “mutant”

Question 9

Co-dominance

Answer 9

Both alleles of the gene are expressed (e.g. AB blood type)

Question 10

Incomplete dominance

Answer 10

An intermediate phenotype is expressed (e.g. Rr = pink flowers)

Question 11

What is the product of meiosis

Answer 11

4 haploid daughter cells

Question 12

Daughter cells

Answer 12

Germ cells

Question 13

Germ cells

Answer 13

Give rise to gametes in organisms that sexually reproduces

Question 14

What is the process of meiosis

Answer 14

DNA replication -> meiosis I -> meiosis II

Question 15

How is genetic diversity introduced in meiosis?

Answer 15

Recomination (cross-over) of homologous chromosomes and independent assortment

Question 16

Recombination/cross-over of homologous chromosomes

Answer 16

Homologs exchange genetic material (same genes represented but different combination of alleles) before being split into daughter cells in synapsis

Question 17

How do meiosis differ from mitosis?

Answer 17

1. Meiosis productes 4 haploid (1n) daughter cells
2. Daughter cells are genetically distinct from parent
3. 2 rounds of division (meiosis I and II)
4. Germ cells produced
5. Recombination between homologous chromosomes

Question 18

What is different about the meiosis and mitosis process?

Answer 18

In prophase 1 of meiosis, a tetrad forms by synapsis of homologous chromosomes and crossing over occurs

Question 19

Synapsis

Answer 19

Pairing of homologous chromosomes

Question 20

Tetrad

Answer 20

Pairs of homologous chromosomes connected by synapsis (4 total chromatids) and crossing over occurs

Question 21

What types of recombination can occur?

Answer 21

Single cross over (one point in tetrad) or double crossover (two points in tetrad)

Question 22

Chiasma

Answer 22

Physical link between chromatids of homologous chromosomes during recombination

Question 23

Non-disjunction

Answer 23

When homologous chromosomes or sister chromatids do not separate correctly during meiosis OR mitosis resulting in aneuploidy

Question 24

Law or segregation

Answer 24

A parent has 2 alleles per gene but only passes 1 allele onto the next generations

Question 25

Law of independent assortment

Answer 25

The alleles of one gene separate into daughter cells independently of the alleles for another gene (ie. The way gene A is sorted is random and independent of how gene B is sorted)

Question 26

What is the exception to the law of independent assortment?

Answer 26

Linkage

Question 27

Linkage

Answer 27

Genes that are close to each other on a chromosome are more likely to be inherited together (ie. Linked)

Question 28

Rf

Answer 28

Recombination frequency is a quantification of genetic linkage

Question 29

What does a large Rf value mean

Answer 29

The genes are further apart --> more likely to crossover --> independently assorted

Question 30

How do you calculate Rf?

Answer 30

Rf = the # of recombinant offspring/total # of offspring

Question 31

What does an Rf of 1 cM mean?

Answer 31

1% chance that those genes will cross over

Question 32

At what Rf value does independent assortment occur?

Answer 32

>/= 50%

Question 33

SRY gene

Answer 33

A gene in the sex-determining region on Y chromosomes that causes undifferentiated gonads to develop into testes instead of ovaries

Question 34

If no SRY gene is present

Answer 34

Gonads develop into ovaries (female = default sex)

Question 35

Examples of X-linked recessive disorders

Answer 35

Color blindness, hemophilia, muscular dystrophy

Question 36

Cytoplasmic inheritance

Answer 36

Inheritance of gene found outside of nuclear DNA (mitochondrial and chloroplasts have their own DNA)

Question 37

Hemizygous

Answer 37

Only one copy of the gene or DNA is present in diploid cells (e.g. mitochondrial DNA which is passed from mothers only)