Chapter 7: Cellular Replication and variation

Question 1

What is meiosis?

Answer 1

A two phase-type of cellular division to form 4 daughter cells

Question 2

What are sex cells called?

Answer 2

Gametes

Question 3

What is a locus?

Answer 3

The position a gene occupies in a chromosomes

Question 4

What are homologous chromosomes?

Answer 4

Two copies of the same gene, not always the exact same

Question 5

What is an allele?

Answer 5

Small differences in DNA sequence forming a different form from the other homologous chromosome

Question 6

What is a genotype?

Answer 6

The alleles present in the cell of an organism. (Yy)

Question 7

What is a karyotype?

Answer 7

Order by length, smallest to largest, display of homologous pairs (sister chromatids, joined at the centromere). One from father and one from mother. Page 141

Question 8

What are matched sex chromosomes called?

Answer 8

Autosomes

Question 9

What are females chromosomes and males chromosomes?

Answer 9

Females (XX), Males (Xy)

Question 10

What is diploid?

Answer 10

Describes an organism comprising of two copies of each chromosome, 2n

Question 11

What is a haploid?

Answer 11

Describes an organism comprising of one copy of each chromosome, n

Question 12

What reduces chromosome numbers from (diploid) 2n to (haploid) n?

Answer 12

Meiosis, to produce egg and sperm

Question 13

What produces chromosome numbers back to 2n from n?

Answer 13

Fertilisation to form a zygote

Question 14

Where does Meiosis occur in plants?

Answer 14

Female and male parts

Question 15

Where does Meiosis occur in animals?

Answer 15

Ovaries and testes

Question 16

What happens at interphase?

Answer 16

DNA replication occurs resulting in sister chromatids attached at the centromere

Question 17

What is the process of meiosis?

Answer 17

prophase, metaphase, anaphase and telophase

Question 18

What is the process of prophase I?

Answer 18

Chromatin shortens and thicken, a spindle begins to form and attached to the centromere of each chromosome, homogenous chromosomes lie side by side (synapsis), they may coil around each other (now bivalent (visible)), later they move apart but non-sister chromatids remain in contact (chiasmata) and finally the nuclear membrane breaks now

Question 19

What happens at metaphase I?

Answer 19

Homologous chromosomes move together to line up, still attached at chiasmata

Question 20

What happens in anaphase I?

Answer 20

Maternal and paternal chromosomes are pulled towards opposite polls of homologous chromosomes by spindle fibres, sister chromatids remain joined at the centromere and move towards the same poll, the disjunction of each homologous pair happens independently of the others.

Question 21

What happens in telophase I?

Answer 21

A haploid set of chromosomes can be seen at each poll, each chromosome still having a sister chromatid, the spindle breaks down, the cell starts to split and cytokinesis completes the first stage.

Question 22

What happens at the end of meiosis I and before meiosis II?

Answer 22

Interphase, but DNA does not replicate

Question 23

What happens in prophase II?

Answer 23

A new spindle forms

Question 24

What happens in metaphase II?

Answer 24

Chromosomes move to the equator of the cell

Question 25

What happens in anaphase II?

Answer 25

Sister chromatids separate and move to polls, chromatids become the chromosomes of daughter cells a

Question 26

What happens in telophase II?

Answer 26

Spindle disappears, chromosomes de-condense, cytoplasmic division follows resulting in 4 haploid cells. Page 143

Question 27

Describe the process of crossing over and recombination

Answer 27

During synapsis in prophase 1, the non-sister chromatids become attached at points called chiasmata. They exchange genetic material (crossing over), this recombination scrabbled the genetic material and rearranges the combinations of alleles on each homologous chromosome. This produces new genes and increases the genetic diversity of offspring. Page 144

Question 28

what is oogenesis?

Answer 28

The process in the ovary that results in the production of female gametes

Question 29

What is spermatogenesis?

Answer 29

The continuous production of sperm cells in the testis

Question 30

Differences between oogenesis and spermatogenesis?

Answer 30

In oogenesis, cytokinesis in both meioses is unequal and produced 1 egg. Spermatogenesis produced 4 sperm in contrast. At birth women have all eggs to ever mature, men produce sperm at puberty. Sperm is produced continuously, whereas oogenesis has long breaks that can take more than 40 years between the beginning and end of meiosis I.

Question 31

What happens at fertilisation?

Answer 31

Haploid cells fuse to create a diploid zygote. n to 2n

Question 32

What is an independent assortment?

Answer 32

Maternal and paternal chromosomes act independently from homologous pairs during meiosis ensuring a mixture of maternal and paternal DNA

Question 33

What does independent assortment do?

Answer 33

Increases the number of different combinations of genes, increase variety of children

Question 34

What is random fertilisation?

Answer 34

Meiosis and fertilisation shuffle existing alleles into different combinations increasing the potential for different genotypes