Inheritance

Question 1

define a gene

Answer 1

A gene is a sequence of nucleotides/ DNA that codes for a specific polypeptide

Question 2

define a allele

Answer 2

A particular version of a gene
eg. Blood type in humans

Question 3

what are the 2 types of alleles?

Answer 3

Dominant and recessive alleles

Question 4

what are dominant alleles?

Answer 4

• Dominant alleles are always expressed when present
• written using upper-case
  Aa> dominant allele is A

Question 5

what is a recessive allele?

Answer 5

• only expressed is the dominant allele is not present
• written using lower-case letters

Question 6

how many chromosomes does a human cell have?

Answer 6

46 chromosomes, that are divided into 23 pairs of homologous chromosomes

Question 7

what are homologous chromosomes?

Answer 7

• they have the same gene on the same loci
• they may or may not have the different alleles
  > shape : two ears on both sides and one little circle in the middle

Question 8

what is a genotype?

Answer 8

AA, aa, Aa,

Question 9

what are the genotype for homozygous dominant chromosomes?

Answer 9

AA

Question 10

what are the genotype for Heterozygous chromosomes?

Answer 10

Aa, aA

Question 11

what is the genotype for homologous recessive chromosomes?

Answer 11

aa

Question 12

define phenotype?

Answer 12

appearance,
colour?, skin colour, curly hair?, spots

Question 13

can the environment change ur phenotype?

Answer 13

Yes! our phenotype can change with effects to the environment
eg. when provided with better education system, a person can become more intelligent,

Question 14

methods to find the offspring outcomes for a cross between 2 parents

Answer 14

using a punnet square, or the use of genetic diagrams

Question 15

Draw a punnet square and predict the outcomes!
BB x Bb

Answer 15

1:1
All offspring will show dominant trait

Question 16

Draw a punnet square and predict the outcomes!
Bb x Bb

Answer 16

1:2:1
BB:Bb:bb
3:1
dominant trait: recessive trait

Question 17

What are the 2 types of variation?

Answer 17

Discontinuous and Continuous variation

Question 18

What is Discontinuous variation?

Answer 18

• has distinct categories/groups
• affected by one or a few genes only
  -not affected by the environment
  eg. Sickle cell haemoglobin, dimples, ABO blood group, double eyelid

https://scienceaid.net/images/6/63/variation.png

Question 19

What is continous variation?

Answer 19

• has no distinct categories
• affected by many genes
• affected by the environment
  eg. Height, weight, skin tone, intelligence

https://scienceaid.net/images/6/63/variation.png

Question 20

what are the 2 types of selection

Answer 20

natural and artificial selection

Question 21

what is natural selection?

Answer 21

selective reproduction success due to natural factors

Question 22

what is artificial selection?

Answer 22

Selective reproductive success due to human interference/choice

Question 23

what is meant by variation in a population?

Answer 23

refers to variation in the characteristics and traits between individuals in a population.

Question 24

State a way genetic variation can arise in a population?

Answer 24

Mutation

Question 25

which sex chromosomes does a male have?

Answer 25

XY chromosomes

Question 26

which sex chromosomes does a female have?

Answer 26

XX chromosomes

Question 27

Define mutation

Answer 27

Mutation is the spontaneous/ random change to the structure of a gene or chromosome number.

Question 28

What causes mutation?

Answer 28

- Radiation (UV light/gamma rays) - mutagens

Question 29

can mutations be inherited?

Answer 29

Mutations in stomatic cells are not inherited, but mutagens in gametes can be inherited Stomatic cells: all cells accept sex cells

Question 30

What are gametes

Answer 30

Human sex cells

Question 31

What are the 2 types of mutation

Answer 31

Gene mutation and Chromosome number mutation

Question 32

What is Gene mutation?

Answer 32

it is the change in nucleotide sequencing resulting in a different polypeptide being produced eg. Sickle cell anaemia

Question 33

What is sickle cell anaemia? (for content)

Answer 33

Red blood cells normally produce normal haemoglobin that can bind to oxygen and carry oxygen to other parts of the body. If the haemoglobin gene is mutated, the normal haemoglobin protein cannot be formed In sickle cell anaemia, there is a mutation in the Hb gene due to a change in the nitrogenous base sequence. The result is sickle cell haemoglobin (HbS) which cannot bind to oxygen normally. Instead under low O2 conditions, it will polymerize and bind to the cell surface membrane, and cause the RBC to change shape, into sickle cell, becoming very fragile and inelastic. Sickle cells die/burst very easily. If a person has many sickle cells the death of these cells means they lose O2 carrying capacity. Thus those suffering from sickle cell disease generally have more difficulty breathing than others, and die more easily

Question 34

Explain gene mutation using a named example?(olevel qn)- 4m

Answer 34

Gene mutation is a spontaneous/random change in the nitrogenous base sequence. An example of gene mutation is sickle cell anaemia. The haemoglobin gene is mutated and produces abnormal haemoglobin that causes the red blood cells to become sickle shaped and burst more easily. Th oxygen carrying capacity of blood is decreased.

Question 35

What is chromosome number mutation?

Answer 35

it is the change in chromosome number due to non-disjunction of homologous chromosomes during meiosis (cell division) sister chromatids failing to separate during cell division. eg. Down syndrome( Trisomy 21)

Question 36

What is down syndrome?

Answer 36

In human cells, there are normally 46 chromosomes (23 from the father and 23 from the mother) When gametes are formed during meiosis, the homologous chromosomes pair up, then split up into different cells so that each gamete daughter cell receives only 23 chromosomes. If there is non-disjunction of chromosome 21(gamete) during meiosis, one gamete will have 24 chromosomes instead of 23, it will have an extra copy of chromosome 21.

Question 37

how does down syndrome occur?

Answer 37

- Egg cell with 23 chromosomes+ sperm cell with 24 chromosomes - Egg cell with 24 chromosomes+ sperm cell with 23 chromosomes

Question 38

what are the chemicals that have alot of radiation causing mutations?

Answer 38

UV light and Gamma rays