2.3 DNA and Inheritance

Question 1

What is DNA made up of

Answer 1

Two long chains of alternating sugar and phosphate molecules twisted to form a double helix

Question 2

Complementary base pairing (which goes with which)

Answer 2

Adenine goes with Thymine
Cytosine goes with Guanine

Question 3

How does the order of bases determine proteins made

Answer 3

The order of bases forms a code which determines the order in which different amino acids are linked to form proteins

Question 4

Triplet code

Answer 4

3 bases = 1 triplet - codes for 1 amino acid

Question 5

What does genetic profiling do

Answer 5

Shows similarity between 2 DNA samples

Question 6

Genetic profiling steps

Answer 6

1. A sample of cells is collected, The cells are broken up and the DNA extracted
2. The DNA is cut up by enzymes into fragments of different sizes
3. The fragments are separated into bands by order of length using electrophoresis
   A pattern develops, this is the genetic profile

Question 7

Uses of genetic profiling

Answer 7

Multiple patterns - genetic profiles - are compared
- Identify someone who has left DNA at a crime scene
- Determine a child’s paternity
- Comparisons between species for classification
- identify the presence of genes that are associated with a certain disease so precautions can be taken

Question 8

Gene definition

Answer 8

A length of DNA that codes for one protein

Question 9

Allele defintion

Answer 9

A variety of a gene - different version of the same gene e.g. gene for eye colour: one allele for blue, one allele for brown

Question 10

Chromosome

Answer 10

A length of DNA containing many genes, found in the nucleus

Question 11

Genotype

Answer 11

The genetic makeup of an individual in terms of alleles

Question 12

Phenotype

Answer 12

The way the genotype is expressed

Question 13

Dominant allele

Answer 13

That allele that always shows itself in the phenotype whenever it is present

Question 14

Recessive allele

Answer 14

The allele that only shows itself in the phenotype when dominant allele is not present (hidden when dominant is present)

Question 15

F1/F2

Answer 15

First generation/Second generation in a genetic cross

Question 16

Homozygous/homozygote

Answer 16

A homozygote contains 2 identical alleles for the gene concerned e.g. BB, bb

Question 17

Heterozygous/heterozygote

Answer 17

A homozygote contains 2 different alleles for the gene concerned e.g. Bb

Question 18

Selfing

Answer 18

Pollen from a plant fertilises ovules in a flower of the same plant

Question 19

Gamete

Answer 19

a sex cell

Question 20

Pure breeding

Answer 20

Always produce one type of offspring - homozygous

Question 21

How many alleles from each pair of alleles is passed into a gamete

Answer 21

Only one

Question 22

If 2 pure breeding parents are crossed, what do the F1 offspring show

Answer 22

All show the dominant characteristic (Bb)

Question 23

If 2 F1 are crossed, ratio of F2 that show the dominant:recessive characteristic

Answer 23

3:1

Question 24

When sperm and egg cells combine, there is a __% chance of male/female offspring

Answer 24

50%

Question 25

What is genetic modification (GM) (GMO = genetically modified organism)

Answer 25

Artificial transfer of genes from one organism to another

Question 26

GMO advantages

Answer 26

• crops tailored to suit varied farming condition
  provides more nutritional value
• provides higher income
• higher yield
• fewer chemicals needed
• energy producing crops - save natural resources and the environment

Question 27

GMO disadvantages

Answer 27

• reduce reliance on developing countries
• companies developing GMO could patent - control price - too expensive
• difficult to stop GM pollen from pollinating nearby crops or escaping into environment (e.g. cause weeds to have herbicide resistance)