Genetics

Question 1

What is the difference between asexual and sexual reproduction and how do they work

Answer 1

Asexual - a type of reproduction involving only one parent. It uses the process of mitosis to create identical copies of the parent cell
Sexual - the formation of new organisms by combining the genetic material of two organisms. It uses the process of meiosis, which creates gametes

Question 2

What are facts about asexual reproduction

Answer 2

Requires one parent
Offspring is identical to parent
Takes a shorter time
Takes less energy
Unable to adapt to surroundings

Question 3

What are facts about sexual reproduction

Answer 3

Requires two parents
Offspring is unique to the parent
Takes a longer time
Takes more energy
Able to adapt to surroundings

Question 4

What are gametes

Answer 4

Sex cell

Sperm in males and eggs in females (animals)
Pollen in males and eggs in females (flowering plants)

Question 5

What are zygotes

Answer 5

A fertilised egg cell

Question 6

What is fertilisation and how does it work

Answer 6

The fusion of the nucleus of a male gamete with the nucleus of a female gamete

When the two gametes combine, they merge the two sets of chromosome to have 46
This produces a new cell called a zygote, which will mature into an embryo. The number of cells increase by mitosis, and as the embryo develops, the cells begin to differentiate

Question 7

What is DNA, how many strands does it have and what shape is it

Answer 7

The material inside the nucleus of cell carrying the genetic information
2
A double helix

Question 8

What are chromosomes

Answer 8

Long threads of DNA which is made up of many genes

Question 9

What a gene

Answer 9

A small section of DNA in a chromosome

Question 10

What an allele

Answer 10

Different version of the same gene

Question 11

What is the difference between a genotype and a phenotype

Answer 11

Genotype - the characteristic an organism has, usually written in letters
Phenotype - the characteristic an organism has, usually written in words

Question 12

What is the difference between a dominant and recessive allele

Answer 12

Dominant - will show a characteristic if inherited from one or both parents. Represented by a capital letter
Recessive - will show a characteristic if inherited from both parents. Represented by a lowercase letter

Question 13

What is the difference between a homozygous dominant, homozygous recessive and heterozygous

Answer 13

Homozygous dominant - a genotype with two dominant alleles, e.g. AA
Homozygous recessive - a genotype with two recessive alleles, e.g. aa
Heterozygous - a genotype with on dominant and recessive allele, e.g. Aa

Question 14

What are the sex chromosomes for males and females

Answer 14

Males - xy
Females - xx

Question 15

What is Cystic Fibrosis and how is it inherited

Answer 15

An inherited genetic disease that mainly affects the lungs and digestive system
Caused by a recessive allele. Both parents have to be carriers for their child to have a chance of inheriting it

CC - not affected by CF
Cc - carrier of CF
cc - affected by CF

Question 16

What is Polydactyly and how is it inherited

Answer 16

An inherited condition in which a person has extra fingers or toes
By a dominant allele. Only one parent needs to have it for their child to have a chance of inheriting it

PP - affected by polydactyly
Pp - affected by polydactyly
pp - not affected by polydactyly

Question 17

What are the genetic tests

Answer 17

Antenatal - to analyse an individual’s DNA or chromosomes before they are born
Neonatal - analysing a sample of blood that is taken from pricking a baby’s heel
Pre-implantation genetic diagnosis - the embryos are checked to see if they have any particular conditions before implantation in IVF

Question 18

What are the limits of genetic testing

Answer 18

False positive - A genetic test that wrongly detected a certain allele or faulty chromosome
False negative A genetic test has failed to detect a certain allele or faulty chromosome

Question 19

What are the sources of variation

Answer 19

Genetic - some features can be passed on from your parents, e.g. eye colour and blood group
Environment - some features can be influenced by your surroundings, e.g. hair colour, scars and tattoos
Combined - e.g. weight, height and behaviour

Question 20

What are the types of variation

Answer 20

Continuous - a range of values which can have values in between not in groups, e.g. height, weight, milk yield
Shown as a line graph or histogram

Discontinuous - data that comes in groups and not a range, e.g. blood group and eye colour
Shown as a bar chart

Question 21

What is the difference between variation and mutation

Answer 21

Variation - within genes that lead to different genotypes, and this can be seen by a different phenotype
Mutation - a change in a gene or chromosome

Question 22

What is selective breeding and how does it work

Answer 22

When humans breed plants and animals for particular genetic characteristics

Decide which characteristics are important enough to select
Choose parents that show these characteristics from a mixed population. They are bred together.
Choose the best offspring with the desired characteristics to produce the next generation
Repeat the process continuously over many generations, until all offspring show the desired characteristics

Question 23

What are some characteristic you want in plants and animals

Answer 23

Plants:
Disease resistance in food crops
Wheat plants that produce a lot of grain
Large flowers

Animals:
Animals that produce a lot of milk and meat
Chickens that lay large eggs
Domestic dog that have a gentle nature

Question 24

What are the benefits and risks of selective breeding

Answer 24

Benefits:
New varieties may be economically important, by producing more or better quality foods
Animals can be selected so that they don’t cause harm, e.g. a cattle without horns

Risks:
Reduced genetic variation can make the susceptible to the same disease/insects
Can create physical problems due to something not forming right

Question 25

What is a genetic engineering and how does it work

Answer 25

A scientific technique in which a gene is moved from one organism to another to give it the desired characteristics

Select the desired characteristics
The gene responsible for the characteristic is cut out of the chromosome using enzymes
The gene is transferred and inserted into another organism

Question 26

What is genetic engineering currently used for

Answer 26

Diabetes - bacterial cells have been genetically modified to produce substances such as human insulin
GM crops - resistant to insect attack or are herbicide resistant

Question 27

What are advantages and disadvantages of genetic engineering

Answer 27

Advantages:
GM bacteria producing human insulin that can be used to treat diabetes
Improve crop yields or crop quality, which is important in developing countries. This may help reduce hunger around the world

Disadvantages:
Transfer of the selected gene into other species. What benefits one plant may harm another
Pollen produced by the plants could be toxic and harm insects that transfer it between plants

Question 28

What is natural selection

Answer 28

The natural process whereby the best-adapted individuals survive longer, have more offspring and thereby spread their characteristics

Question 29

How does natural selection work

Answer 29

Variation is caused by a mutation
Competition for a food and resource
Individuals with the mutation have the survival advantage and survive
Survivors breed and pass genes to their offspring

Question 30

What is the fossil record and why is it incomplete

Answer 30

A collection of fossils
Fossils provide a snapshot of the past and allow us to study how much or how little organisms have changed as life developed on Earth

Many early forms of life were soft-bodied, which means that they have left few traces behind
Geomorphic processes break them

Question 31

What are the ways we can see evidence of evolution

Answer 31

Fossils - a preserved remain or trace of a dead organism
Casts and impression - formed when an organism is buried in soft sediment and decays leaving a cast of itself
Gradual replacement - teeth and bones slowly decay and are replaced by minerals
Amber - fossilised tree sap covers the organism and there is no oxygen or moisture so microbes that cause decay can’t survive
Glaciers - it is too cold for the microbes that cause decay to work
Peat bogs - it is too acidic for microbes to decay

Question 32

What is an example of evidence for evolution

Answer 32

Antibiotic resistance

Mutations occur in the genes of individual bacterial cells
Some mutations protect the bacterial cell from the effects of the antibiotic
Bacteria without the mutation die or cannot reproduce when the antibiotic is present
Resistant bacteria can reproduce with less competition from normal bacterial strains

Question 33

How can antibiotic resistance be avoided

Answer 33

Doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections
Patients should always complete the full course of antibiotics to ensure all bacteria are killed and none do not survive to mutate and form resistant strains
The agricultural use of antibiotics should be restricted

Question 34

What is extinction and what are some factors that cause it

Answer 34

There are no remaining individuals of a species alive

New diseases
New predators
New, more successful competitors
Changes to the environment over geological time, such as climate change
A single catastrophic event, such as a massive volcanic eruption or a collision between an asteroid and the Earth

Question 35

How are organisms classified

Answer 35

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 36

How has technology changed classification

Answer 36

Microscopes, biochemistry, genome mapping and DNA evidence enhanced the classification system by allowing scientists to take a closer look at organisms