Genetics

Question 1

Describe 2 advantages of asexual reproduction

Answer 1

1. Requires 1 parent (No need to find a mate)
2. Offspring can be produced very quickly due to the reproductive cycle

Question 2

Explain a disadvantage of asexual reproduction

Answer 2

No genetic variation, meaning if environmental conditions become unfavourable, the whole population may be affected, less chance of survival.

Question 3

Explain an advantage of sexual reproduction

Answer 3

Introduces genetic variation into the population, meaning if there was an environmental change, some species would have more chance of survival.

Question 4

Describe 2 disadvantages of sexual reproduction

Answer 4

1. Takes long periods of time, less offspring can be produced
2. Two parents needed, can be a problem for isolated individuals

Question 5

Describe the cells produced by meiosis.

Answer 5

Produces 4 genetically different daughter cells, called gametes. They are haploid cells (Half genetic material).

Question 6

Why are haploid cells produced via meiosis.

Answer 6

So when they fuse with another gamete (sex cell), the cell will have the full genetic material of a normal cell.

Question 7

Describe the structure of DNA

Answer 7

They are polymers made up of nucleotides (A sugar, phosphate and base). Two strands of DNA are coiled into a double-helix shape.

Question 8

How are DNA strands held together to form a double helix shape

Answer 8

The strands are linked by a series of complementary base pairs
joined together by weak hydrogen bonds

Question 9

Describe the word Genome

Answer 9

The entire DNA of an organism

Question 10

Describe the word Gene

Answer 10

A section of DNA which codes for a protein

Question 11

Explain the stage of protein synthesis, Transcription

Answer 11

RNA polymerase binds to non-coding DNA located in
front of a gene.
Double helix structure of DNA uncoils leaving exposed bases.
RNA polymerase produces a complementary mRNA
strand from the coding DNA of the gene.
mRNA leaves to enter cytoplasm via a nuclear pore.

Question 12

Explain the stage of protein synthesis, Translation

Answer 12

mRNA attaches to a ribosome.
Each three bases in the mRNA is a codon, 1 codon codes for 1 amino acid. tRNA brings amino acid the the mRNA, along with anti-codons to compliment the codons on the mRNA. Chain of amino acids form, known as a polypeptide. The tRNA detaches, and the polypeptide chain folds up, forming a protein

Question 13

Define the terms: A) Chromosome
B) Allele

Answer 13

A) Chromosomes in the nucleus are made from genes which are made from DNA

B)Alleles are different versions of the same gene

Question 14

Define the terms: A) Dominant
B) Recessive

Answer 14

A) An allele which is always present (Shown) even if only one copy is present.

B) Only expressed if the individual has two copies and does not have the dominant allele of that gene

Question 15

Define the terms: A) Homozygous
B) Heterozygous

Answer 15

A) Homozygous alleles are both identical for the same characteristic, for example AA or aa.

B) Heterozygous alleles is when an individual has different alleles for a particular gene.

Question 16

Define the terms: A) Genotype
B) Phenotype

Answer 16

A) An organisms complete set of genetic material

B)The visible characteristics in an individual resulting from the expression of genes

Question 17

Define the terms: A) Gamete
B) Zygote

Answer 17

A) A haploid sex cell produced by meiosis

B) Formed by the fusion of two gametes

Question 18

Explain the practical for extracting DNA from fruit (6)

Answer 18

1. Mash some strawberries, put them in a beaker with a solution of detergent and salt.
2. The detergent will break down the cell membranes to release dna.
3. Filter the mixture to get the froth and insoluble bits of the cell out.
4. Slowly add some ice cold alcohol.
5. The dna will come out of the solution, it is not soluble in cold alcohol. It will appear as a stringy white precipitate.
6. Fish it out with a glass rod.

Question 19

Why does the order of bases matter in the translation stage of protein synthesis

Answer 19

Each codon, 3 bases, codes for a specific protein, that has a particular job. The body would not function efficiently if we did not have ordered codons

Question 20

Describe how genetic variants in the non coding region of dna can affect the phenotype of a person

Answer 20

May give a person different alleles, as a different protein is coded for, giving them different visible characteristics (such as brown instead of black hair). These are known as mutations.

Question 21

Give 1 reason why it was difficult for people to fully understand Mendel’s work at the time of discovery

Answer 21

Scientists didn’t have the background knowledge to fully understand his findings. They had no idea about genes and DNA.

Question 22

Explain why humans have differences in their inherited characteristics due to alleles

Answer 22

Some alleles are dominant, and some are recessive. Different one’s are shown for every person. Every person has a different genome (the makeup of our alleles), hence our differing characteristics.

Question 23

What do genetic diagrams, punnet squares and family pedigrees show

Answer 23

The chance an offspring has of a certain characteristics

Question 24

Describe how the sex of offspring is determined at fertilisation

Answer 24

If a female receives the y chromosome from the male, offspring will be male. If a female receives the x chromosome, offspring will be female.

Question 25

Which blood group shows co-dominance and why

Answer 25

AB, both alleles are dominant, so both are expressed at the same time

Question 26

Which blood group is the:

A) Universal donor
B) Universal recipient

Answer 26

A) O
B) AB

Question 27

Alleles for blood types A and B are always dominant. State the only way someone can inherit blood type O.

Answer 27

Offspring receives the blood type O allele from both parents.

Question 28

Explain how you can inherit a sex linked genetic disorder

Answer 28

Passed down from parents on either the X or Y chromosomes.

Question 29

Why are males more likely to develop sex linked genetic disorders than females

Answer 29

Males only have one Y chromosome, meaning they often only have one allele for sex linked genes. Because males only have one, even if the allele is recessive it will be shown

Question 30

How is most of your phenotype presented

Answer 30

as a result of multiple genes rather than single gene inheritance

Question 31

Describe 2 causes of variation that influence one’s phenotype

Answer 31

1. genetic variation – different characteristics as a result of mutation and sexual reproduction
2. environmental variation – different characteristics caused by an organism’s environment (acquired characteristics)

Question 32

Is there much genetic variation amongst a population. If so, state why

Answer 32

there is usually extensive genetic variation within a
population of a species and these arise through mutations

Question 33

Why may some genetic mutations not change one’s phenotype

Answer 33

The mutation may still code for the same protein, causing no difference

Question 34

Genetic mutations may have 3 effects. State each

Answer 34

No effect, benefit, disadvantage

Question 35

Describe the outcomes of the human genome project

Answer 35

20500 genes have been located
1800 genes related to disease have been found

Question 36

Describe potential applications of the human genome project within medicine

Answer 36

Prediction and prevention of diseases, testing and treatment for inherited disorders, new medicines