Topic 3 Genetics

Question 1

Sexual reproduction

Answer 1

2 parents - 50% DNA from mother, 50% from father

Question 2

Asexual reproduction

Answer 2

1 parent - clones itself and is genetically identical

Question 3

Advantages of sexual reproduction

Answer 3

Variation in population, leads to natural selection and evolution, better adapted to environment, if environment changes then more individuals likely to survive

Question 4

Disadvantages of sexual reproduction

Answer 4

Need to find a mate, takes more time and energy, fewer offspring, need to attract and find mates, isolated individuals will have to walk far

Question 5

Advantages of asexual reproduction

Answer 5

Don’t need to find a mate, rapid reproduction cycle

Question 6

Disadvantages of asexual reproduction

Answer 6

No variation in population, if conditions become unfavourable then whole population affected

Question 7

Haploid cell

Answer 7

Sperm and egg, 23 chromosomes

Question 8

Diploid cell

Answer 8

Body cell/zygote = 46 chromosomes

Question 9

Fertilisation

Answer 9

Process where 2 gametes fuse DNA together to produce a zygote which then undergoes mitosis and develops into an embryo - mixture of chromosomes

Question 10

Meiosis

Answer 10

Cell duplicates its DNA.
Chromosomes line up in the middle.
Some of mother’s chromosomes and father’s chromosomes go into each cell as they divide.
2nd division, chromosomes line up again and arms pulled apart - each cell has mixture of chromosomes, important for genetic variation
4 gametes made, all genetically different with single set of chromosomes

Question 11

Chromosomes

Answer 11

Tightly wound up long length of DNA that contains hundreds of genes each that code for a specific protein

Question 12

Where is genetic information found?

Answer 12

In nucleus of every cell in 23 pairs of chromosomes

Question 13

Gene

Answer 13

A short section of a chromosome that codes for a specific protein that is used in your body
One gene - one protein
Multiples genes can work together to make a single phenotype

Question 14

Complementary base pairs

Answer 14

Adenine - Thymine

Cytosine - Guanine

Question 15

Structure of DNA

Answer 15

Polymer of two strands coiled to form a double helix
Strands linked by a series of complementary base pairs joined together by weak hydrogen bonds
Nucleotides that consist of sugar and a phosphate group with one of 4 bases attached to sugar

Question 16

Genome

Answer 16

Entire DNA of an organism

Question 17

Extracting DNA from fruit

Answer 17

Mash fruit and put in detergent and salt solution - detergent breaks down cell membrane and salt sticks DNA together.
Filter mixture and put in boiling tube in beaker of hot water so the enzymes denature, add pentose and leave for 1 min.
Add ice-cold alcohol to mixture and DNA will appear as white precipitate

Question 18

Genotype

Answer 18

Gene type e.g RR, rr, Rr

Question 19

Phenotype

Answer 19

Characteristic e.g brown hair, depends if genotype is dominant or recessive

Question 20

Allele

Answer 20

Different version of the same gene

Each person has 2 - one from father and one from mother

Question 21

Dominant phenotype

Answer 21

Occurs when one has at least 1 dominant allele e.g RR, Rr

Question 22

Recessive phenotype

Answer 22

Occurs when one has 2 recessive alleles e.g rr

Question 23

Homozygous genotype

Answer 23

Same allele twice e.g RR, rr

Question 24

Heterozygous genotype

Answer 24

Two different alleles e.g Rr

Question 25

Punnet Square

Answer 25

R ¦ r
——————
R ¦ RR ¦ Rr
r ¦ Rr ¦ rr
3/4 dominant phenotype, 1/4 recessive phenotype
Ratio for unaffected:carrier:disorder is 1:2:1

Question 26

Heterozygous genotype in letters

Answer 26

Bb

Question 27

Homozygous recessive genotype in letters

Answer 27

bb

Question 28

Homozygous dominant genotype in letters

Answer 28

BB

Question 29

Proof there is a 50% chance of having a female or male

Answer 29

X ¦ X
——————
X ¦ XX ¦ XX
Y ¦ XY ¦ XY

Question 30

Pedigree analysis

Answer 30

An affected person of a recessive disease will always have genotype ‘bb’ (homozygous recessive).
A carrier of a recessive disease will always have genotype ‘Bb’ (heterozygous)
An unaffected person of a recessive disease will always have genotype ‘BB’ (homozygous dominant)

Question 31

Causes of variation that influence phenotype

Answer 31

Genetic variation - different characteristics as a result of mutation and reproduction, e.g eye colour
Environmental variation - different characteristics caused by an organism’s environment (acquired characteristics), e.g language
Most phenotypes are a result of both e.g weight

Question 32

Human Genome Project

Answer 32

Mapping of all genes in the human genome

Question 33

Advantages of Human Genome Project

Answer 33

Prediction and prevention of diseases so people can get best advice for their lifestyle and they can get regular checkups.
Testing and treatment for inherited disorders through identifying faulty alleles
Find out how individual bodies will react to certain diseases and possible treatments for them, drugs can be designed for people with a genetic variation

Question 34

Disadvantages of Human Genome Project

Answer 34

Increased stress for people susceptible to some diseases
People with genetic disorders may come under pressure not to have children
Discrimination by employers and life insurance to people who are more likely to get a disease

Question 35

What are extensive genetic variations caused by in a population?

Answer 35

Mutations

Question 36

Mutations main effects

Answer 36

Most have no effect on phenotype, some have small affect and rarely, some have significant effect

Question 37

NO TRIPLE CONTENT HERE

Answer 37

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