4B- Diversity and selection

Question 1

Diploid (2n)

Answer 1

• cell contains 2 copies of each chromosome

- 23 pairs 64 chromosomes humans

Question 2

chromosomes of each pair have

Answer 2

• same size

- same genes but different alleles

Question 3

Homologous pairs

Answer 3

• pair of chromosomes with the same genes but may have different alleles
• same size chromosomes and same genes but can have different alleles

Question 4

homozygous

Answer 4

2 copies of the same allele at the same locus

Question 5

Heterozygous

Answer 5

2 different alleles at the same locus

Question 6

locus

Answer 6

• position on a chromosome where a particular allele is found
• alleles coding for the same characteristic found at same fixed position on each chromosome

Question 7

haploid (n)

Answer 7

contain 1 copy of a chromosome from an homologous pair gamates

Question 8

How does fertilisation cause genetic diversity

Answer 8

random any sperm fertilises any egg producing zygote with different combinations of chromosomes from each parent

Question 9

Meiosis

Answer 9

1-DNA unravels and replicates so 2 chromatids produced (2 copies of each chromosome)
2-DNA condenses to from double armed chromosomes made from sister chromatids joined by centriomere
3-M1- chromosomes arrange in homologous pairs and separated
4-M2- sister chromatids separate as centromere divides
5-4 genetically different haploid daughter cells

Question 10

Crossing over of chromatids

Answer 10

1-M1-homologous chromosomes pair up
2-Chromatids twist around each other
3- equal lengths of chromatids exchange alleles
4-same genes but different combinations of alleles
5-4 daughter cells have chromatids with different alleles

Question 11

Independent segregation of Chromosome

Answer 11

1-M1 homologous chromosomes separated

2-random which chromosome from each homologous pair ends up in which daughter cell

Question 12

Meiosis variation

Answer 12

1-random fertilisation
2-crossing over of chromosomes
3-independent segregation

Question 13

Mitosis difference from meiosis

Answer 13

1-Diploid
2-genetically identical
3-2 daughter cell
4-1 division

Question 14

Meiosis difference from mitosis

Answer 14

1-haploid
2-genetically different
3-4 daughter cell
4-2 division

Question 15

degenerate

Answer 15

-same amino acids coded for by more than 1 base triplets

Question 16

universal

Answer 16

-same base triplets code for same amino acids in all organisms

Question 17

Mutagenic agents

Answer 17

increase the rate of mutations arising

Question 18

mutations are always

Answer 18

spontaneous random

Question 19

chromosome non disjunction

Answer 19

failure of chromosomes to separate properly