Biology unit 17 and 18

Question 1

Define gene

Answer 1

As a length of DNA that codes for a protein

Question 2

Define allele

Answer 2

As an alternative form of a gene

Question 3

Chromosomes

Answer 3

Are made of DNA which contains genetic info in the form of genes

Question 4

Sequence of bases

Answer 4

The sequence of bases in a gene determine the sequence of amino acid used to make a specific protein

Question 5

How protein is made

Answer 5

• The gene coding for the protein remains in the nucleus
• Messenger RNA 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 basis in the mRNA

Question 6

Describe mitosis

Answer 6

As a nuclear division giving rise to genetically identical cells

Question 7

uses of Mitosis

Answer 7

• cell division giving rise to genetically identical cells
• used from growth repair and replacing cells and asexual reproduction
• during mitosis the DNA/chromosomes replicate then the cell divides

Question 8

Describe stem cells

Answer 8

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

Question 9

Define meiosis

Answer 9

Is involved in the production of gametes

Question 10

Describe meiosis

Answer 10

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

Question 11

uses of Meiosis

Answer 11

• used for making sex cells/gametes
• Produces 4 haploid daughter cells
  with half the chromosome number
  of a regular body cell
  -This is because at fertilisation the
  two haploid gametes will fuse,
  making the zygote diploid

Question 12

Describe inheritance

Answer 12

As the transmission of genetic information from generation to generation

Question 13

Describe genotype

Answer 13

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

Question 14

describe phenotype

Answer 14

As the observable features of an organism

Question 15

Describe homozygous

Answer 15

As having two identical alleles of a particular gene

Question 16

Describe heterozygous

Answer 16

As having two different alleles of a particular gene

Question 17

Describe co dominance

Answer 17

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

Question 18

Describe sex linked characteristics

Answer 18

As 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 the other

Question 19

Describe red-green colour blindness

Answer 19

As an example of sex linkage

Question 20

Describe variation

Answer 20

As the differences between individuals of the same species

Question 21

Describe gene mutations

Answer 21

As a random change in the base sequence of DNA

Question 22

Describe adaptive feature

Answer 22

As an inherited feature that helps an organism to survive and reproduce in its environment

Question 23

Describe adaptation

Answer 23

As the process resulting from, natural selection by which populations become more suited to their environment over many generations

Question 24

Describe the development of strains of antibiotic resistant bacteria

Answer 24

As an example of natural selection

Question 25

selective breeding

Answer 25

1. Humans select individual organisms with desirable traits e.g high yields and quality produce
2. Cross/breed these individuals together to try and combine their traits
3. Produce large numbers of offspring. Select the individuals with the combination of desired traits
4. Repeat over many generations