Cell Division And Sex Determination

Question 1

Two ways in which cells are produced in our body

Answer 1

Mitosis and meiosis

Question 2

Mitosis ( Function, where it occurs, stages, daughter cells)

Answer 2

Function: Growth, repair, and replacement of damaged cells
Asexual reproduction
Where: In damaged and worn out cells
In asexually reproducing organism
Stages: interphase: chromosomes number doubles
DNA from nucleus splits in a singular division
Daughter cells: 2 genetically identical daughter cells that are clones of their parents
And are diploid cells ( 46 chromosomes, 23 pairs) , identical to parents
In mitosis, parent cells divide once to produce 2 genetically identical diploid daughter cells

Question 3

Meiosis ( function, where it occurs, stages, daughter cells)

Answer 3

Function: to create genetically diverse offsprings
Where: in human reproductive organs, ovaries and testes
Produced genetic variation
Stages: fertilization: female and male gametes fuse to forms. Zygote with diploid
2 rounds of division occur to reduce to haploid
Daughter cells: 4 genetically diverse diploid cells are produced
In meiosis, after 2 divisions, 4 genetically unique haploid cells are produced, and they are called gametes bcs they are haploid

Question 4

Asexual reproduction with one example

Answer 4

Requires only one parents, and does not involve the fusion of gametes
The offspring produced is genetically identical to the parent
Example: bacteria reproduced by binary fusion
But in this mutation of DNA occurs so it’s not always genetically identical

Question 5

Sexual reproduction

Answer 5

Involves two parents, fusion of the gametes occurs that were produced by meiosis
Offsprings are genetically different to the parent, due to receiving only half from each and due to random fusion of gametes , creating genetic variation

Question 6

How is Sex determined

Answer 6

The 23rd pair of chromosomes are the sex chromosomes, all women have XX chromosomes and all men have XY chromosome, there fore the gender of the offspring is determined by the male

Question 7

How are the sex organs formed

Answer 7

The single Y chromosomes in male is transcribed and translated into a protein which results in a development of testes, which then produces the male sex hormones Causing male characteristics
In females, as they lack the genes, so they develop ovaries, which produced female sex hormones

Question 8

What is the ratio of a male and female offspring

Answer 8

Using a punnet square we can determine that 50% of each sex is the possibility

Question 9

Gene

Answer 9

Short sequences of DNA on chromosomes , that code for a specific polypeptide

Question 10

Allele

Answer 10

Alternative version of gene

Question 11

Dominant

Answer 11

Only one dominant allele is needed to determine the phenotype, characteristic expressed in an organism

Question 12

Recessive

Answer 12

Only determines the phenotype, if there are 2 copies of these alleles

Question 13

Heterozygous

Answer 13

If an individual has two different alleles of that gene

Question 14

Homozygous

Answer 14

If an individual has two Alleles of a gene that are the same

Question 15

Genotype

Answer 15

The combination of alleles

Question 16

Phenotype

Answer 16

The visible characteristics as a result of the alleles

Question 17

Chromosomes

Answer 17

Condensed strands of DNA, all our genetic material is held in 23 pairs of chromosomes

Question 18

Mono hybrid cross

Answer 18

A mono hybrid cross is a diagram that shows you the possible genetic combinations from two parents for a single trait

Question 19

When one parent is heterozygous and one is homozygous recessive

Answer 19

Child has 1:1 ratio of heterozygous and homozygous recessive

Question 20

If both parents are homozygous dominant

Answer 20

Then all 4 offspring possibilities are homozygous dominant

Question 21

If both parents are homozygous recessive

Answer 21

All 4 offsprings are homozygous recessive

Question 22

Inherited conditions - what is Polydactyly, How is it caused in terms of genotype

Answer 22

Polydactyly is a condition in which babies are born with extra toes and fingers
It is caused by Dominant Allele, this means even if you inherited one Gene allele it can cause the disease
If a child has the disease, then one parent must have the disease
If mother has Dd, and dad is dd
Crossing it means there is 1:1 ratio of child having the disease ( Dd)

Question 23

Cystic Fibrosis

Answer 23

Is caused by recessive Allele, and causes difficulty in breathing and digestive problems
These problems occur because a thick sticky mucus is produced which blocks passageways around the lungs and pancreas
Here 2 copies of recessive allele must be inherited
So the child must be homozygous recessive for it to be inherited

Question 24

Who is a carrier

Answer 24

A carrier is the one who is heterozygous for a trait, they carry one recessive and one dominant allele, the carrier will be asymptomatic

Question 25

How does a family pedigree diagrams work

Answer 25

Family pedigree illustrates inheritance of genetic disorders
Women : Circle. Male: Square
Shaded: those who expressed the trait
Half shaded: a carrier ( heterozygous )