Meiosis

Question 1

What condenses into chromosomes before cell division?

Answer 1

Chromatin network

Question 2

What do chromosomes consist of ?

Answer 2

DNA and protein

Question 3

What is a haploid cell?

Answer 3

a cell where their is only one set of chromosomes

Question 4

What is a diploid cell?

Answer 4

A cell where their is double set of chromosomes

Question 5

What are gametes?

Answer 5

Sex cells

Question 6

What are somatic cells?

Answer 6

Body cells (diploid)

Question 7

What are gonosomes?

Answer 7

Sex chromosomes

Question 8

What are autosomes?

Answer 8

Chromosomes not responsible for sex determination

Question 9

What are homologous chromosomes?

Answer 9

A pair of chromosomes inherited from each parent, same genes from same parent

Question 10

What is cytokinesis?

Answer 10

Division of cytoplasm during cell division

Question 11

What occurs during interphase of meiosis?

Answer 11

Dna replication
chromosomes turn from single to double thread
Each chromosome will now consist of two chromatids joined by centromere

Question 12

What does DNA replication help with ?

Answer 12

Double genetic material so it can be shared by new cells arising from cell division

Question 13

What is meiosis?

Answer 13

The type of cell division that only occurs in sex organs to produce gametes

Question 14

What is meiosis also known as ?

Answer 14

Reductive division

Question 15

True or false ? After meiosis the daughter cells are identical to mother

Answer 15

FALSE

Question 16

What happens in meiosis 1?

Answer 16

number of cells double
chromosomes half

Question 17

What happens in meiosis 2?

Answer 17

number of chromosomes do not get reduced

Question 18

Describe Prophase 1?

Answer 18

Chromatin network condenses and threads shorten and thicken to become visible as chromosomes
Homologous chromosomes arrange themselves in pairs
Chromatids from each homologous chromosome overlap (crossing over)
Chiasma (the point of overlap)
Genetic material exchanged between homologous chromosomes
nucleus and nuclear membrane disappear

Question 19

Describe Metaphase 1?

Answer 19

Chromosomes line up along equator of the cell as homologous pairs
Homologous chromosomes attach to spindle fibre using centromere
Random Assortment occurs

Question 20

Describe Anaphase 1?

Answer 20

Spindle fibre shortens separating the homologous chromosomes as they move to opposite poles of the spindle

Question 21

Describe Telophase 1?

Answer 21

Spindle fibre disappears
Nuclear membrane and nucleolus forms
Cytokinesis occurs
Two daughter cells formed with half chromosomes of mother

Question 22

What are two ways that meiosis increases genetic variation?

Answer 22

Crossing over
Random Segregation

Question 23

Describe crossing over

Answer 23

Homologous pairs come together
Crossing over and segments of chromatids swapped
DNA swapped between chromatids that came from mother and father
Results in mixing of genetic materials
Chromatids still contain same genes but different alleles of genes

Question 24

Describe Random Segregation

Answer 24

Daughter cells have different combinations of chromosomes
Human cells have combination of chromosomes from mother and father
Gametes are formed , different combinations of maternal and paternal genes go into each gamete

Question 25

Describe Prophase 2

Answer 25

Spindle fibre reforms nucleolus and nuclear membrane disappear Each chromatid consists of two chromatids joined at centromere

Question 26

Describe Metaphase 2

Answer 26

Chromosomes attach to spindle fibre using the centromere Each chromosome lines up randomly on. the equator independently of how other chromosomes line up

Question 27

Describe Anaphase 2

Answer 27

spindle fibre shortens and splits centromere of each chromosome Two chromatids are pulled to opposite poles of cells Therefore Anaphase 2 is separation of chromosomes

Question 28

Describe Telophase 2

Answer 28

Spindle fibre disappears Nuclear membrane and nucleolus form Cytokinesis occurs Four daughter cells formed with half chromosomes of mother Four cells genetically different

Question 29

Result of meiosis

Answer 29

Four daughter cells genetically different from mother cell and each other containing haploid number of chromosomes

Question 30

Significance of meiosis

Answer 30

Chromosome number is halved Ensures genetic variation

Question 31

What disorder is resulted from an extra chromosome?

Answer 31

Down's Syndrome

Question 32

Characteristics of Down's Syndrome

Answer 32

flat face slanted eyes abnormal ears short, stubby fingers and toes mentally handicapped poorly developed heart and lungs shortened life span

Question 33

How does Down's Syndrome occur?

Answer 33

Non-disjunction occurs ; failure of chromosomes separating correctly During Anaphase 1 of meiosis, chromosome pair 21 does not separate 24 chromosomes move to one pole and 22 to the other Sperm combine with egg cell to form zygote where there are three 21 chromosomes As zygote develops into and embryo all cells will have extra chromosome

Question 34

What is gaining of an extra chromosome known as ?

Answer 34

Trisomy

Question 35

True or False? Chances of having a down's syndrome baby increases exponetially with age a woman falls pregnant

Answer 35

TRUE

Question 36

How to prevent Down' Syndrome?

Answer 36

Pregnant women has a sample of amniotic fluid extracted from uterus with a syringe and tested by pathologist. Process known as amniocentesis