Inheritance

Question 1

Genome

Answer 1

The entire DNA of an organism

Question 2

Gene

Answer 2

A section of DNA which codes for a particular protein

Question 3

What does the nucleus of a cell contain?

Answer 3

Chromosomes on which genes are located

Question 4

DNA molecule

Answer 4

Two strands coiled to form a double helix, the strands being linked by a series of bases: Adenine with Thymine, and Cytosine with Guanine

Question 5

RNA molecule

Answer 5

Single stranded and contains Uracil instead of Thymine

Question 6

Transcription

Answer 6

When two strands of DNA double helix are separated. One strand is used as a template and the RNA bases are lined up in correct order using complementary base pairing.

Question 7

Translation

Answer 7

Involves assembling amino acids in correct order following the sequence of bases on mRNA. It takes place at one of many small structures in the cell cytoplasm called ribosomes. The mRNA travels out of the nucleus and attaches to a ribosome.

Question 8

Protein synthesis

Answer 8

The code for making the protein is read such that every three bases on the mRNA codes for one amino acid. This triplet of bases is know as a codon. Amino acids are carried to the ribosome by another molecule called tRNA which also has a triplet of bases called an anticodon and this can match up with the complementary bases on the mRNA. The ribosome then forms peptide bonds between the amino acids and a polypeptide chain is formed. This can then fold and join up with other polypeptides to form a protein.

Question 9

Alleles

Answer 9

Alternate forms of a gene which give rise to differences in inherited characteristics

Question 10

Dominant

Answer 10

Allele of a gene that is expressed in the heterozygote

Question 11

Recessive

Answer 11

Allele that is not expressed in the phenotype when a dominant allele is present (i.e. the heterozygote)

Question 12

Homozygous

Answer 12

Genotype with the same allele of a gene e.g. AA or aa

Question 13

Heterozygous

Answer 13

Genotype with different alleles of a gene e.g. Aa

Question 14

Phenotype

Answer 14

How a gene is expressed. The “appearance” of an organism resulting from its genotype

Question 15

Genotype

Answer 15

Alleles an organism has for a certain characteristic

Question 16

Codominance

Answer 16

Pattern of inheritance where neither allele of a gene is dominant over the other so that both alleles are expressed in the phenotype

Question 17

What are most phenotypic features a result of?

Answer 17

Polygenetic inheritance rather than single genes

Question 18

What is our sex determined by?

Answer 18

The presence of the Y chromosome, XX in a female and XY in a male

Question 19

Prophase

Answer 19

Before mitosis the DNA replicates and chromosomes formed 2 exact copies called chromatids. In prophase the chromatids become visible, joined at a centromere. The nuclear membrane breaks down.

Question 20

Metaphase

Answer 20

A structure called the spindle forms. The chromosomes line up at the “equator” of the spindle, attached to it by centromeres.

Question 21

Anaphase

Answer 21

The spindle fibres shorten and pull the chromatids to opposite ends (“poles”) of the cell. The chromatids separate to become the chromosomes of the two daughter cells.

Question 22

Telephase

Answer 22

Two new nuclei form at the poles of the cell. The cytoplasm starts to divide to produce two daughter cells. Both daughter cells have identical sets of chromosomes.

Question 23

When does mitosis occur?

Answer 23

During growth, repair, cloning and asexual reproduction

Question 24

What does the division of a cell by meiosis produce?

Answer 24

Four cells, each with half the number of chromosomes, this results in the formation of genetically different haploid gametes

Question 25

What does random fertilisation produce?

Answer 25

Genetic variation of offspring

Question 26

What is the diploid number in human cells?

Answer 26

46

Question 27

What is the haploid number in human cells?

Answer 27

23

Question 28

What causes variation within a species?

Answer 28

Genes, environment or both

Question 29

Mutation

Answer 29

A rare, random change in genetic material that can be inherited

Question 30

How can a change in DNA affect the phenotype?

Answer 30

By altering the sequence of amino acids in a protein

Question 31

ATT TCC GTT ATC ATT TTC CGT TAT C

Answer 31

Duplication

Question 32

ATT TCC GTT ATC ATT CCG TTA TC

Answer 32

Deletion

Question 33

ATT TCC GTT ATC ATG TCC GTT ATC

Answer 33

Substitution

Question 34

ATT TCC GTT ATC ATT CCT GTT ATC

Answer 34

Inversion

Question 35

Why do most genetic mutations have no change?

Answer 35

The same amino acids is coded for because multiple codons code for the same amino acid (Substitution, Inversion)

Question 36

Why do some genetic mutations have a small effect?

Answer 36

One amino acid changes (Substitution, Inversion)

Question 37

Why do genetic mutations rarely have a significant effect?

Answer 37

The protein changes (Duplication, Deletion)

Question 38

What can increase the incidence of mutations?

Answer 38

Exposure to ionising radiation (e.g. gamma rays, X-ray and UV) and some chemical mutagens (e.g. tobacco)

Question 39

What is the process of natural selection?

Answer 39

- Individuals in a species show variation that is caused by differences in genes - Individuals with a characteristic that is advantageous in the environment have a higher chance of survival - Surviving individuals are more likely to reproduce and so are more likely to pass on their advantageous alleles - Over many generations the advantageous characteristics become more common in the population

Question 40

How can antibiotic resistance increase in bacterial populations?

Answer 40

- A random mutation can give rise to a new bacterial allele that code for antibiotic resistance - When the bacterial population is exposed to an antibiotic any individuals without the resistant allele die, while those with the resistant allele survive - The surviving bacteria are more likely to reproduce, passing on their resistant alleles their offspring - Over several generations the frequency of the resistant allele increases, eventually resulting in an antibiotic resistant strain of bacteria

Question 41

Why is antibiotic resistance a problem?

Answer 41

Bacteria can only be treated with the application of a different antibiotic; in some cases several antibiotics need to be used to treat a resistant infection. Antibiotic resistance therefore makes bacterial infections more difficult to control