Patterns and Principles of Heredity

Question 1

What is meiosis?

Answer 1

Formation of gametes that involves cell division to half the chromosome number

Question 2

When does it occur?

Answer 2

After S (synthesis) phase of the cell cycle so:
- divide pairs of chromosome types
- divide sister chromatids

Question 3

What are the two division events?

Answer 3

meiosis 1= reductive division (chromosome number reduced)
meiosis 2= separation of sister chromatids

Question 4

What is meiosis 1?

Answer 4

the division of homologous pairs of chromosomes
preceded by S phase (cells replicate their DNA)

replicated DNA
doesn’t contain 2 sister chromatids joined by centromere
simplified to one set of chromosomes.

Question 5

Describe the process of Prophase 1

Answer 5

chromosomes begin to pair up
maternal and paternal chromosomes make a tetrad
chromosomes condense
homologous pair & form synaptonemal complex
homologous recombination

Question 6

Describe the process of Metaphase 1

Answer 6

Each pair oh homologous line up at equator
centromeres don’t divide
orientation is random

Question 7

Describe Anaphase 1

Answer 7

chromosomes move to separate poles
remain together at the centromere

Question 8

Describe Telophase 1

Answer 8

Cell division occurs
2 new daughter cells each contain one chromosome
each daughter cell contains different chromosomes

Question 9

Describe Metaphase 2

Answer 9

individual chromosomes line up at metaphase plate
along middle of cells

Question 10

Describe Anaphase 2

Answer 10

Centromeres split
Chromatids separate to separate poles
Chromosomes separated from the centromere

Question 11

Describe Telophase 2

Answer 11

Each daughter cell contains one chromosome of each type
4 haploid daughter cells
all genetically different

Question 12

Why are all the daughter cells genetically different?

Answer 12

because of homologous recombination

Question 13

What is the particulate theory of inheritance?

Answer 13

Characters are distinct ad hereditary determinants
2 genes for each character
members of gene pair segregate equally
fusion of gametes restored pair of genes and is random
different genes assort independently in gametes

Question 14

Define: gene

Answer 14

basic unit of biological information, specific segment of DNA that encodes a protein

Question 15

Define: allele

Answer 15

alternative forms of a gene

Question 16

Define: genotype

Answer 16

alleles at locus

Question 17

Define: phenotype

Answer 17

observable characteristics

Question 18

Define: homozygote

Answer 18

identical (YY) allels at a locus

Question 19

Define: heterozygote

Answer 19

different (Yy) alleles at locus

Question 20

Define: F1

Answer 20

first filial (son or daughter) generation after a cross

Question 21

Define: F2

Answer 21

second generation after a cross

Question 22

What work did Gregor Mendel carry out?

Answer 22

breeding pea plants and noticed 2 different phenotypes

Question 23

Monohybrid Cross

Answer 23

Yy x Yy = YY Yy Yy yy
fertilisation restored the two copies of gene to offspring
offspring genotype combination specific alleles that they carry
Dominant and recessive alleles

Heterozygous Yy x Yy will always create 3:1 ratio

Question 24

Dihybrid Cross

Answer 24

AaBb x AaBb
A- found on long chromosome
B- found on short chromosome
Two different genes that control different phenotypes

Pair up in prophase1
equal probability of recessive or dominant lining up together- random process with formation of 4 haploid cells

Heterozygous RrYy x RrYy will always create 9:3:3:1 ratio of phenotypes

Question 25

What is the Law of segregation?

Answer 25

two alleles for each trait separate during gamete formation and then reunite ar random, one from each parent, during fertilisation.

Question 26

What is the Law of Basic Probability?

Answer 26

Transmission of alleles follows this principle

Question 27

What is the Law of Independent Assortment?

Answer 27

Genes assort independently during the formation of gametes