Chapter 3- Genetics- Meosis

Question 0

(State that meiosis is a reduction division of diploid nucleus to form haploid nuclei:)
Most sexually reproducing animals are diploid which means?

Answer 0

They have to copies of every 2 copies of every chromosome (one maternal origin one paternal)

Question 1

(State that meiosis is a reduction division of diploid nucleus to form haploid nuclei:)
-what is the process of meiosis?

Answer 1

Process by which sex cells (gametes) are made in the reproductive organ

Question 2

(State that meiosis is a reduction division of diploid nucleus to form haploid nuclei:)
In order to reproduce organisms need gametes that are?

Answer 2

Haploid (have only one copy of each chromosome)

Question 3

(State that meiosis is a reduction division of diploid nucleus to form haploid nuclei:
The fertilisation of 2 gametes results in?

Answer 3

Formation of a diploid zygote

Question 4

(State that meiosis is a reduction division of diploid nucleus to form haploid nuclei:)
Meosis consists of 2 cell divisions what are they?

Answer 4

1st division= reduction devision of the diploid nucleus to form haploid nucleus
2nd division= separates sister chromatids

Question 5

What do homologous chromatids share?

Answer 5

The same structural feature. (Eg size, pattern)

The same genes at the same loci positions (genes= some alleles might be different)

Question 6

How many cells does Meosis produce?

Answer 6

4

Question 7

What is the 1st stage of Meosis?

Answer 7

‘S’ phase of interphase- DNA replication

Question 8

Why does DNA replication occur in the first stage of Meosis?

Answer 8

To make a copy of its genetic information during interphase–> results in each chromatid having an identical copy or sister chromatid attach to it at the centromere

Question 9

Draw the crossing over diagram in Meosis

Answer 9

Fucking do it you have a week.

Question 10

What 4 things happens in prophase 1?

Answer 10

1) chromosomes become visible as DNA compacts (super coiling)
2) homologous chromosomes are attracted to each other and pair up–> one from father, one from mother
3) crossing over occurs between non-sister chromatids
4) spindle fibres made from microtubles form

Question 11

What 2 things happens in metaphase 1

Answer 11

1) bivalents (another name for homologous pairs of chromosomes) line up across cell equator
2) nuclear membrane disintegrates

Question 12

What 1 thing happens in anaphase 1?

Answer 12

1) spindle fibres from the poles attach to chromosomes and pull them to opposite poles of the cell

Question 13

What 2 things happen in telophase 1?

Answer 13

1) spindles and spindle fibres disintegrate

2) usually the chromosomes uncool and new nuclear membrane forms

Question 14

What happens at the end of Meosis 1?

Answer 14

Cytokines

Question 15

What happens in cytokines 1?

Answer 15

Cell split into 2 separate cells
Cells=haploid because only contain 1 chromosome of each pair
Now Meosis 2 can take place in order to separate sister chromatids

Question 16

What 2 things happens in prophase 2?

Answer 16

1) DNA condenses into visible chromosomes again

2) new meiotic spindle fibres are produced

Question 17

What 3 things happen in metaphase 2?

Answer 17

1) nuclear membrane disintegrates
2) individual chromosomes line up along the equator of each cell, in random orientation
3) spindle fibres from opposite poles attach to each of the sister chromatids at the centromere

Question 18

What 4 things happen in anaphase 2?

Answer 18

1) centromeres of each chromosomes splits, releasing each sister chromatid
2) spindle fibres pull individual chromatids to opposite ends of cell
3) because of the Radom orientation- chromatids coul be pulled towards either of the newly forming daughter cells
4) 2^23 possibilities

Question 19

What 2 things happen in telophase 2?

Answer 19

1) chromosomes unwind their strands of DNA

2) nuclear envelopes form around each of the 4 haploid cells preparing them for cytokines

Question 20

Definition of non-disjunction

Answer 20

Chromosomes failing to separate properly resulting in extra gametes 1 or 1 missing (aneuploidy)

Question 21

How may non-disjunction occur? And how does it affect daughter cells?

Answer 21

• failure of homologous to separate during anaphase 1 resulting in 4 Affected daughter cells
• failure of sister chromatids to separate during anaphase 2 affecting 2 daughter cells

Question 22

3 copies of chromosome 21 (trisomy 21) means?

Answer 22

Makes Down syndrome

Question 23

Give an example of how parents can result in a child having 3 chromosomes 21

Answer 23

One parents gametes has 2 copies of chromosome 21 as a result of non-disjunction the other parent has 1 copy of chromosome 21 and when fusedd together zygote has 3 copies of chromosome 21

Question 24

In karyotyping how are chromosomes arranged?

Answer 24

Arranged into homologous pairs and displayed according to their structural characteristics and go down in size

Question 25

How are chromosomes able to be seen in karyotyping?

Answer 25

Involves harvesting cells (usually from foetus or white blood cells of adult) and chemically inducing cell division but stopping it dying meiosis when chromosomes are condensed and visible they are then stained and photographed before arranging them into structure

Question 26

What is karyotyping tend to be used for?

Answer 26

Determine sex of child

Test for chromosomal abnormalities

Question 27

What are the 2 ways of getting chromosomes with karyotyping?

Answer 27

Amniocentesis and chorionic villus sampling

Question 28

What happens during Amniocentesis?

Answer 28

Needle inserted through abdominal wall into amniotic cavity in the uterus and a sample of amniotic fluid containing foetal cells is taking

Question 29

How far in the pregnancy can amniocentesis happen? And what is the chance of miscarriage?

Answer 29

16th week

~0.5%

Question 30

What happens in chorionic villus sampling?

Answer 30

Tube is inserted through the cervix and a tiny sample of chorionic villi (contains foetal cells) from placenta is taken

Question 31

What chromosomes show a male/female?

What shows if it has Down syndrome?

Answer 31

Male= X Y female= X X

Down syndrome= 21sr chromosome has 3