Topic 6 - Variation, evolution and inheritance

Question 1

What does sexual reproduction involve?

Answer 1

Fusion of male and female gametes - produced my meiosis.

Question 2

What is the male and female gamete in humans?

Answer 2

Male - Sperm
Female - Egg

Question 3

What is the male and female gamete in plants?

Answer 3

Male - Pollen
Female - Egg

Question 4

What happens the the DNA in sexual reproduction?

Answer 4

Mixes DNA from each parent creating a variation in their offspring.

Question 5

What is asexual reproduction carried out by?

Answer 5

All bacteria, some plants and few animals.

Question 6

What is the difference between asexual reproduction and sexual reproduction?

Answer 6

No gametes only one parent cell.
No mixing of DNA so no variation in offspring.
Relies of mitosis instead of meiosis to produce genetically identical clones of parent.

Question 7

What are the stages in meiosis

Answer 7

1) Before the cell starts to divide it duplicates in genetic information and become x shaped.
2) Then the parent cell divides once and half the number of chromosomes into two cells.
3) Then a second division occurs where each x shaped chromosome is split down the middle.
4) 4 genetically different haploid daughter cells are produced.

Question 8

What are the differences between mitosis and meiosis?

Answer 8

Question 9

What happens to the two haploid gametes during fertilisation?

Answer 9

The two haploid gametes (23 chromosomes each) fuse and the full number of chromosomes is restored to form a diploid zygote.

Question 10

What are advantages and disadvantages of asexual reproduction?

Answer 10

Only one parent needed so fast and less energy needed.
No genetic variation in offspring so less likely to be able to survive environmental change.
Can produce many identical offspring when conditions are favourable.

Question 11

What do genes code for?

Answer 11

A particular sequence of amino acids.

Question 12

Define genome.

Answer 12

All the genetic material in an organism.

Question 13

Why was the human genome project very important?

Answer 13

It has and will continue to improve our understanding of genes linked with different types of inherited disorders.

Question 14

What is DNA and what is it made of?

Answer 14

DNA is a polymer made up of 2 strands of four different nucleotide monomers.

Question 15

What decides the order of amino acids in a gene?

Answer 15

The order of bases.

Question 15

What are the four different bases in DNA?

Answer 15

T
A
C
G

Question 16

What are the two bases that always pair with each other and what is it called?

Answer 16

A and T
C and G
Complementary base pairing

Question 17

What does mRNA do and how is it made?

Answer 17

Carries the code to the ribosome.
Made by copying code from DNA.

Question 18

After the protein chain is formed what happens?

Answer 18

It folds to produce a unique shape. The shape is specific to its function as an enzyme, hormone or structural protein - are physically strong for example collagen.

Question 19

What are mutations?

Answer 19

Changes to the DNA base sequence.
They occur continuously.
Rarely a mutation will code for an altered protein.

Question 20

What is a gene?

Answer 20

A short section of DNA that codes for a protein.

Question 21

Define a allele.

Answer 21

Different versions of a gene that give a certain characteristic.

Question 22

What is a genotype?

Answer 22

The alleles an organism has for a particular gene

Question 23

What is a phenotype?

Answer 23

The observable characteristics an organism has based on genotype.

Question 24

What are the three main types of genotypes?

Answer 24

Homozygous recessive Heterozygous Homozygous Dominant

Question 25

What is homozygous recessive and how is it represented?

Answer 25

Both alleles in this genotype are recessive. It is represented by two lower case letters to represent alleles.

Question 26

What is homozygous dominant and how is it represented?

Answer 26

Where both alleles are dominant alleles. It is shown in diagrams as 2 Capital letters.

Question 27

What is heterozygous?

Answer 27

When there is one dominant and one recessive allele. It.

Question 28

How is a dominant allele represented in a phenotype?

Answer 28

A dominant allele is always expressed in the phenotype if at least one copy is present in the genotype.

Question 29

How is a recessive allele represented in a phenotype?

Answer 29

Recessive alleles need 2 copies to be expressed in the phenotype.

Question 30

Do this punnet square and work out the percentage of a red flower.

Answer 30

75%

Question 31

How are inherited diseases caused?

Answer 31

Caused by mutations in certain alleles which are then passed down from parents to offspring

Question 32

How does cystic fibrosis work and who are the carriers?

Answer 32

Caused by a recessive allele. Need two copies of recessive allele to have the disorder. Heterozygous genotypes are carriers.

Question 33

How does polydactyly work any carriers?

Answer 33

Gives you extra fingers/toes. Caused by a dominant allele. Only need one copy to have the disorder. No carriers as heterozygous have it.

Question 34

What is embryo screening?

Answer 34

Embryo screening is a process used to check embryos for genetic disorders or genetic traits. It is used during in vitro fertilisation (IVF). A cell is removed from an early embryo. The DNA in that cell is tested for specific alleles that may cause genetic diseases (e.g. cystic fibrosis).

Question 35

What are the advantages and disadvantages of embryo screening?

Answer 35

Advantages It will help to stop suffering. Treating disorders costs the government a lot of money. Disadvantages It implies people with genetic problems are undesirable this could increase prejudice. Screening is expensive.

Question 36

Is a sperm allele XY or XX?

Answer 36

XY

Question 37

What is variation?

Answer 37

Differences in characteristics between organisms.

Question 38

How is genetic variation caused?

Answer 38

Random mutation

Question 39

What is variation a result of?

Answer 39

Inherited genes Environment Combination of both

Question 40

What is evolution?

Answer 40

Evolution is the change of inherited characteristics of a population over time and happens through the process of natural selection.

Question 41

Define natural selection.

Answer 41

Where only some organisms with certain characteristics can survive and reproduce in their environment.

Question 42

What did darwin state?

Answer 42

All species alive today evolved from simple life forms.

Question 43

Describe the process of natural selection.

Answer 43

There is variation in the population due to random mutation. Some organisms have characteristics that enable them to survive and reproduce. They pass on alleles for their offspring so there are more in the population. This leads to populations having phenotypes that are best adapted to their environment. If this happens in two populations of the same species they can become so different in their phenotypes that they can no longer breed and produce fertile offspring therefore a new species formed.

Question 44

What is selective breeding?

Answer 44

When humans artificially select plants and animals that are going to breed to obtain desirable characteristics.

Question 45

What are the advantages and disadvantages and disadvantages of selective breeding

Answer 45

Advantages More yield Can improve disease resistance Disadvantages Reduces the gene pool (number of different alleles). This reduces the genetic variation so if a new disease appears all the stock closely related to it will die. Reduces biodiversity.

Question 46

What is genetic engineering?

Answer 46

The transfer of a gene responsible for a desirable characteristic from one organism's genome to another.

Question 47

How is genetic engineering carried out?§

Answer 47

A useful gene is identified (e.g. gene for insulin production). The gene is cut out using enzymes called restriction enzymes. The gene is inserted into a vector (usually a plasmid or virus). The vector is used to transfer the gene into target cells. The cells develop and reproduce with the new characteristic.

Question 48

What are common used of Genetic enginnering?

Answer 48

Genetically modified crops Insulin production Medical research Gene therapy

Question 49

What are advantages and disadvantages of genetic engineering?

Answer 49

Disadvantages They decrease biodiversity Potential long term effects of eating gm crops. Transplanted genes may get into the natural environment. Advantages Increase yield Can give nutrients to nutrient lacking countries. Gm crops are being used in some places often with no problem.

Question 50

What are the two main ways to clone plants?

Answer 50

Tissue culture - few plant cells are put into growth medium and they grow into new plants. Cuttings - Take cutting from parent plant and them plant them to produce genetically identical copies.

Question 51

What are benefits of tissue culture?

Answer 51

Allow scientists to preserve rare plants. They are made very quickly.

Question 52

What is embryonic cloning

Answer 52

Embryonic cloning - Sperm cells are taken from a prize bull and and egg cells are taken from a prize cow. Then they are fertilised. The embryo that develops is split many times to form clones.

Question 53

What did Lamarck find?

Answer 53

Found that characteristics changed during an organisms lifetime and that these were inherited. However this is not true.

Question 54

What were 3 key observations Darwin made?

Answer 54

1) Organisms within a species vary in phenotype. 2) Some individuals with certain characteristics are more likely to survive. 3) Characteristics that enable survival are passed onto the next generation.

Question 55

Why did not everyone agree with Darwin?

Answer 55

It was against religious beliefs. Not much other evidence to convince other scientists.

Question 56

Define speciation.

Answer 56

The formation of two or more species from an original population due to isolation which prevents breeding from individuals in the population.

Question 57

What are the stages in speciation?

Answer 57

1) Population becomes geographically isolated. 2) Isolation prevents breeding and mixing genes. 3) Random mutation occur this causes variation and changes in phenotypes. 4) Natural selection occurs due to different environments. 5) They change so much they can no longer interbreed.

Question 58

What are the three ways fossils can form?

Answer 58

From preservation in places with no decay happening such as amber. Gradual replacement by minerals - hard parts such as bones are replaced by minerals. From casts and impressions

Question 59

Why is the fossil record incomplete?

Answer 59

Many early life forms were soft bodied so all parts decayed. Many fossils have been destroyed by geological activity. Many fossils still undiscovered. Few fossils are made as conditions are rare.

Question 60

What is extinction?

Answer 60

When there are no individuals left alive of the species.

Question 61

What are factors that can cause extinctions.

Answer 61

New diseases New predators New competitors Changes to the environment Catastrophic events Humans causing extinction

Question 62

How does antibiotic resistance occur?

Answer 62

Bacteria undergoes random mutation in their DNA. leading to changes in their characteristics such as antibiotic resistance. Since bacteria reproduce so rapidly they pass on there alleles to offspring.

Question 63

What are ways to reduce antibiotic resistance?

Answer 63

Reduce prescriptions of antibiotics. Patients take full coarse of antibiotics every time. Reduce the use of antibiotics in farm animals.

Question 64

List the order of classification and who was this developed by.

Answer 64

Kingdom Phylum Class Order Family Genus Species Developed by Carl Linnaeus.

Question 65

How do you get the binomial species name?

Answer 65

Use the Genus and the species name.

Question 66

Define species.

Answer 66

A group of similar organisms that can breed to produce fertile offspring.

Question 67

What is the difference between archaea and bacteria?

Answer 67

Archaea = Ancient bacteria Bacteria = true bacteria e.g e.coli