chapter 17

Question 1

Define chromosomes

Answer 1

Made of DNA, which contains genetic information in the form of genes

Question 2

Define a gene

Answer 2

length of DNA that codes for a protein

Question 3

Define allele

Answer 3

Alternative form of gene

Question 4

Define inheritance

Answer 4

Inheritance is the transmission of genetic information from one generation to another

Question 5

Define dominant

Answer 5

an allele that is expressed if it is present

Question 6

Define recessive

Answer 6

an allele that is only expressed when there is no dominant allele of the gene present

Question 7

Define genotype

Answer 7

the genetic make-up of an organism in terms of the alleles present

Question 8

Define phenotype

Answer 8

the observable features of an organisms

Question 9

Define homozygous

Answer 9

having 2 identical alleles of a particular gene . 2 identical homozygous will be pure breeding

Question 10

Define heterozygous

Answer 10

having 2 different alleles of a particular gene. A heterozygous individual is not pure breed

Question 11

where is protein made?

Answer 11

ribosomes, or rough endoplasmic reticulum

Question 12

Protein synthesis involves the process of …

Answer 12

1. transcription ( make mRNA )
2. translation ( translate mRNA to form protein )

Question 13

describe the process of protein synthesis

Answer 13

1. gene on the DNA is copied to form mRNA
2. mRNA moves out of nucleus , to the cytoplasm and ribosomes
3. The mRNA will be passed through the ribosome
4. RIbosome will translate the mRNA and assemble amino acid to form protein

Question 14

Define mitosis

Answer 14

mitosis is the nuclear / cell division giving rise to the genetically identical cells

Question 15

State the role of mitosis in organisms and their importances

Answer 15

1. growth and repair a damaged part of its body
2. replacement worn out cells
3. asexual reproduction
4. important for replacing cells and for allow growth
5. all cells in the body are produced by mitosis of the zygote except gametes

Question 16

describe the process of mitosis

Answer 16

1. each chromosomes make identical copies of itself, DNA content doubled
2. chromosomes line up in the middle of cell
3. Cell fibre will pull them apart forming 2 nuclei each with 1 chromosomes
4. At the end, 2 daughter cells produced are genetically identical to the parent

Question 17

Define stem cells

Answer 17

Unspecialised cells that divide by mitosis to produce daughter cells that become specialised for specific function

Question 18

Define meiosis

Answer 18

The nuclear division in which the chromosomes are halved from diploid to haploid to produce genetically different cells

Question 19

Describe the role of meiosis

Answer 19

The way gametes are produced
Gametes have 1 set of chromosomes instead of 2
When they fuse together, the diploid zygote forms 2 sets of chromosomes

Question 20

Describe the process of meiosis

Answer 20

1. Each chromosome make identical copy of itself with double DNA content
2. Chromosomes pair up in middle of cell , and crossing over occurs, to exchange allele between 2 chromosomes
3. This produces variation
4. Then, cell fibres will pull apart each and new cell will have one of each recombinant chromosome pair. 2 daughter cell formed
5. Chromosomes will line up along centre of cell and cell fibres will pull them apart. A total of 4 genetically different daughter cell produced, with 1 chromosome in each cell

Question 21

Compare mitosis and meiosis

Answer 21

Mitosis Meiosis
genetically identical cell genetically different

2 daughter cell 4 daughter cell

Diploid -> diploid Diploid -> haploid

no variation have variation

for growth , repair
and asexual reproduction in gametes

Question 22

Define codominance

Answer 22

Both allele are equally dominant

Question 23

Examples of codominance

Answer 23

1. snapdragon flower
2. blood group

Question 24

Describe codominance in blood type

Answer 24

Blood type is controlled by 3 allele : A , B , O
O is recessive
A , B dominant

Question 25

Describe the genotypes of blood type A, B , AB, O

Answer 25

A : A A / A O
B : B B / B O
AB : AB
O : OO

Question 26

Define sex-linked characteristic

Answer 26

A feature in which the gene responsible is located on a sex chromosomes and that this makes the characteristic more common in male than female

Alleles found on the X chromosome not the Y chromosomes

Question 27

Examples of sex linked inheritance

Answer 27

Colour blindness
Haemophilia - blood unable to clot

Question 28

Why do males often carry the sex linked condition

Answer 28

Males only have 1 X chromosome, so much more likely to inherit recessive allele and show the condition.

Females have 2 copies of X so likely to inherit one dominant allele that masks the effect of the recessive allele, known as carrier.

Carrier female does not have disease, but have chance of passing recessive allele to offspring, a male.