Chapter 17: Inheritance

Question 1

What are chromosomes made out of

Answer 1

chromosomes are made of DNA, which contains genetic information in the form of genes

Question 2

Define a gene

Answer 2

a length of DNA that codes for a protein

Question 3

Define an allele

Answer 3

as an alternative form of a gene

Question 4

Describe the inheritance of sex in humans with reference to X and Y chromosomes

Answer 4

XY in males and XX in females

Question 5

What is the use of sequence of bases in a gene

Answer 5

the sequence of bases in a gene determines the sequence of amino acids used to make a specific protein

Question 6

Why is the sequence of amino acid important

Answer 6

different sequences of amino acids give different shapes to protein molecules

Question 7

How does DNA control cell function

Answer 7

DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters

Question 8

How is protein made

Answer 8

• the gene coding for the protein remains in the nucleus
• messenger RNA (mRNA) is a copy of a gene
• mRNA molecules are made in the nucleus
and move to the cytoplasm
• the mRNA passes through ribosomes
• the ribosome assembles amino acids into protein molecules
• the specific sequence of amino acids is determined by the sequence of bases in the mRNA

Question 9

Why aren’t all genes expressed

Answer 9

cells in an organism contain the same genes, but many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs

Question 10

Describe a haploid nucleus

Answer 10

a nucleus containing a single set of chromosomes

Question 11

Describe a diploid nucleus

Answer 11

a nucleus containing two sets of chromosomes

Question 12

Describe mitosis

Answer 12

nuclear division giving rise to genetically identical cells

Question 13

State the role of mitosis

Answer 13

• Growth
• Repairing damaged tissues
• Replacing cells that wear out
• Producing new organisms by asexual reproduction

Question 14

What happens before mitosis

Answer 14

the exact replication of chromosomes occurs before mitosis

Question 15

What happens during mitosis

Answer 15

the copies of chromosomes separate, maintaining the chromosome number in each daughter cell

Question 16

Describe stem cells

Answer 16

unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions

Question 17

When is meiosis involved

Answer 17

in the production of gametes

Question 18

Describe meiosis

Answer 18

a reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells

Question 19

Describe inheritance

Answer 19

the transmission of genetic information from generation to generation

Question 20

Describe genotype

Answer 20

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

Question 21

Describe phenotype

Answer 21

the observable features of an organism

Question 22

Describe homozygous

Answer 22

having two identical alleles of a particular gene

Question 23

When does pure breading occur

Answer 23

two identical homozygous individuals that breed together will be pure-breeding

Question 24

Describe heterozygous as

Answer 24

having two different alleles of a particular gene

Question 25

Will heterozygous be pure breeding

Answer 25

a heterozygous individual will not be pure-breeding

Question 26

Describe a dominant allele as

Answer 26

an allele that is expressed if it is present in the genotype

Question 27

Describe a recessive allele as

Answer 27

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

Question 28

Describe codominance

Answer 28

as a situation in which both alleles in heterozygous organisms contribute to the phenotype

Question 29

Explain the inheritance of ABO blood groups:

Answer 29

phenotypes are A, B, AB and O blood groups and alleles are IA, IB and Io

Question 30

Describe a sex-linked characteristic as

Answer 30

a feature in which the gene responsible is located on a sex chromosome and that this makes the characteristic more common in one sex than in the other

Question 31

Example of sex- linkage

Answer 31

red-green colour blindness and hemophilia (male) as the have only one X chromosome