Topic 6: Inheritance, Variation and Evolution

Question 1

What are the benefits of genetic engineering? (3)

Answer 1

1) Can prevent inherited diseases
2) Can reduce cell decay and elongate a human’s life
3) Can improve food production efficiency

Question 2

What are the problems with genetic engineering? (2)

Answer 2

1) Uncertainty over long-term effects - limiting genetic traits or genetic defects
2) Unethical to create new life forms or move genes

Question 3

What are the advantages of genetically modified crops? (4)

Answer 3

1) Make plants resistant to certain insects, herbicides and diseases
2) Crops show increased yield
3) Provide nutrients to diets missing them
4) No complications have been experienced so far

Question 4

What are the disadvantages of genetically modified crops? (3)

Answer 4

1) Can reduce biodiversity by negatively impacting wild flowers and insects
2) Consumption can have long-term effects on human health
3) Transplanted genes may escape into the environment

Question 5

How are insulin-producing bacteria created? (5)

Answer 5

1) Enzymes “cut” the desired (insulin-producing) gene out of a human chromosome
2) Enzymes “cut” a vector (plasmid or virus)
3) Enzymes are used to insert the gene into vector
4) Vector is inserted into required cell
5) If the gene is delivered into an undifferentiated cell, then the organism will have it in it’s genotype and phenotype

Question 6

DNA

Answer 6

The chemical that codes for specific proteins or characteristics

Question 7

Chromosomes

Answer 7

Thread-like structures made up of coiled DNA

Question 8

Gene

Answer 8

A small section of DNA that codes for a particular sequence of amino acids

Question 9

Genome

Answer 9

The entire set of genetic material in an organism

Question 10

Sexual reproduction

Answer 10

The fusion of male and female gametes which causes a mixture of two parents’ genetic information leading to variation in the offspring

Question 11

Asexual reproduction

Answer 11

Reproduction involving one parent where no fusion of gametes or mixing of chromosomes occur leading to genetically identical offspring

Question 12

Dominant allele

Answer 12

An allele which only needs a single copy to be present in the genotype to appear in an organism’s phenotype

Question 13

Recessive allele

Answer 13

An allele which needs two copies to be present in the genotype to appear in an organism’s phenotype

Question 14

Homozygous

Answer 14

When an organism carries two copies of the same allele of a particular gene

Question 15

Heterozygous

Answer 15

When an organism carries two different alleles of a particular gene

Question 16

Genotype

Answer 16

The combination of alleles an organism has for a particular characteristic

Question 17

Phenotype

Answer 17

The physical appearance of an organism

Question 18

Meiosis (6)

Answer 18

First division:
1) Pair of chromosomes replicate
2) They line up at centre of cell and pulled apart
3) Cell divides leaving two cells with a pair of chromosomes and its genes mixed up
Second division:
4) Chromosomes line up at centre of cell and pulled apart
5) Split into a separate arm and move to ends of the cell
6) Cell membrane covers them leaving four genetically different haploid gametes

Question 19

Cystic fibrosis

Answer 19

A genetic disorder of the cell membrane caused by a recessive allele and results in a thick sticky mucus in the air passages

Question 20

Polydactyl

Answer 20

A genetic disorder caused by a dominant allele that results in a baby born with extra fingers

Question 21

Arguments for embryonic screening (3)

Answer 21

1) Stops people suffering
2) Treating disorder costs a lot of taxpayer money
3) There are laws to stop it going to far - can’t even select baby’s sex

Question 22

Arguments against embryonic screening (3)

Answer 22

1) Implies people are undesirable, increasing prejudice
2) Leads to screening for desirable characteristics
3) Expensive

Question 23

Variation

Answer 23

Differences in the phenotypes of organisms caused by their genetics or interaction with the environment

Question 24

Mutation

Answer 24

Rare, random changes that occur continuously in an organism’s DNA that can be inherited

Question 25

The theory of evolution

Answer 25

All living species evolved from simple life forms that developed more than three billion years ago

Question 26

Natural selection (6)

Answer 26

1) Organisms in a species show wide phenotypic variation
2) Organisms in a species compete for limited resources
3) Organisms with the most suitable phenotypes for the environment will be more successful competitors
4) These organisms will be more likely to survive, reproduce and pass on these beneficial phenotypes to offspring
5) Organisms that are less well adapted will be less likely to survive and reproduce
6) Over time beneficial phenotypes will become more common

Question 27

Speciation

Answer 27

When the phenotypes of two populations of one species become so different that they become reproductively isolated so are unable to produce fertile offspring together

Question 28

Evidence for evolution (3)

Answer 28

1) Fossils - shows changes in organisms over time
2) Antibiotic resistance bacteria - supports natural selection
3) Discovery of genetics - explained how characteristics are passed on

Question 29

Reasons for extinction (5)

Answer 29

1) Environmental changes
2) New predator
3) New disease
4) Higher competition
5) Catastrophic event

Question 30

How are fossils formed? (2)

Answer 30

1) When one or more of the conditions for decay aren’t present - glaciers = too cold, amber = no oxygen, peat bogs = too acidic
2) When soft tissues decay and hard bones are replaced by minerals forming rock-like substance

Question 31

Why don’t scientists know how life began? (2)

Answer 31

The fossil record is incomplete because:

1) Early life forms were soft-bodied and have decayed completely
2) Fossils have been destroyed by geological activity

Question 32

Advantages of selective breeding (5)

Answer 32

1) Animals can produce more meat and milk
2) Crops with disease resistance
3) Crops with higher yields
4) Dogs with gentle temperament
5) Decorative plants with big flowers

Question 33

Disadvantages of selective breeding

Answer 33

Reduces gene pool:

1) Inbreeding - prone to inherited defects or diseases
2) Weakness to a new disease for an entire population

Question 34

Reducing antibiotic resistant bacteria

Answer 34

1) Prescription only when needed
2) Completing the full course
3) Restriction of agricultural use of antibiotics

Question 35

Why is the development of new antibiotics unlikely to keep up with new resistant strains?

Answer 35

Development of new antibiotics is slow and costly while bacteria are able to reproduce and evolve rapidly to become resistant

Question 36

Linnaean system

Answer 36

Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 37

Three-domain system

Answer 37

1) Archaea - considered living fossils (as they are survivors of an ancient group of organisms) and are found in extreme living conditions (extremophiles - halophiles, thermophiles and methanogens)
2) Bacteria - true bacteria
3) Eukaryota - broad range of organisms including fungi, plants, animals and protists that have true nuclei