20

Question 1

What is chlorosis?

Answer 1

When the leaves of a plant look pale or yellow

Question 2

Why does chlorosis occur?

Answer 2

As the cells are not producing the normal amount of chlorophyll. This reduces the plants ability to make food by photosynthesis

Question 3

What environmental factors may cause chlorosis?

Answer 3

Lack of light
Mineral deficiencies
Virus infections

Question 4

What is genotype?

Answer 4

The combination of alleles and organism inherits for a characteristic

Question 5

What is phenotype?

Answer 5

The observable characteristics of an organism

Question 6

What are modifications?

Answer 6

The changes an environment makes to a persons phenotype. These are not inherited.

Question 7

What is. A dominant allele?

Answer 7

The version of a gene which will always be expressed if present in an organism.

Question 8

What is a recessive allele?

Answer 8

Only expressed if two copies of this allele are present in an organism.

Question 9

Homozygous genotype?

Answer 9

They have two identical alleles for a characteristic. Can either be homozygous dominant or homozygous recessive.

Question 10

Heterozygous genotype?

Answer 10

They have two different alleles for a characteristic

Question 11

Definition of continuous variation?

Answer 11

A characteristic that can take any value within a range such as height or weight

Question 12

Definition of discontinuous variation

Answer 12

A characteristic that can only appear in specific values such as blood groups

Question 13

Causes of continuous variation?

Answer 13

Genetic and environmental

Question 14

Causes of discontinuous variation?

Answer 14

Mostly genetic

Question 15

What is monogenic inheritance?

Answer 15

Inheritance of a single gene

Question 16

How do you perform a genetic cross?

Answer 16

1) state phenotype of both parents
2) state genotype of both parents
3) state the gametes of each parent, its common to circle letters
4) use Punnett square to show results of random fusion of gametes during fertilisation -> label gametes on edge of square
5) state proportion of each genotype produced among offspring -> either in % or x/y
6)state corresponding phenotype for each possible genotype.

Question 17

What happens in homozygous genetic cross?

Answer 17

• all offspring are heterozygous -> will all have dominant allele
• proven by Mendel using pea pod plants

Question 18

What happens in heterozygous cross?

Answer 18

Ratio is 3:1, dominant to recessive

Question 19

What is codominance? And what is the result?

Answer 19

When two different alleles occur for a gene -> both of which are equally dominant

The result is that both alleles of. The gene are expressed in the phenotype of the organism present.

Question 20

What is an example of codominance?

Answer 20

Snapdragon flowers. Two equally dominant alleles exist, each of which codes for the colour of the flower.

Question 21

Why are upper and lower case letters not used to represent alleles in codominance?

Answer 21

As it would imply one allele is dominant and the other is recessive

Question 22

Multiple alleles

Answer 22

• When some genes have more than two versions of alleles
• As an organism carries only two versions of the gene, only two alleles can be present in an individual.

Question 23

Whats an example of something determined by a gene with multiple alleles?

Answer 23

Blood group -> I^A and I^O are codominant but I^O is recessive

Question 24

How is sex determined?

Answer 24

Females - XX chromosomes on the 23rd pair/sex chromosomes
Males - XY chromosomes on the 23rd pair/sex chromosomes
- sex is determined by whether the sperm fertilising the egg the egg has X or Y chromosome

Question 25

How does X chromosome differ to the Y?

Answer 25

The X chromosome is much larger and contains many genes not involved in sexual development. The Y chromosome is smaller and contains almost no genetic information but carries a gene that allows embryo to develop as a male.

Question 26

What is sex linkage in characteristics?

Answer 26

When some characteristics are determined by genes carried on the sex chromosomes.

Question 27

Why do sex linked characteristics occur?

Answer 27

As the Y chromosome is much smaller than the X and there are a number of genes in the X chromosome that males have only one copy of. Therefore, any characteristic caused by a recessive allele on the section of the X chromosome, which is missing on the Y chromosome, occurs more frequently in males.

Question 28

What are some examples of sex linked disorders?

Answer 28

Haemophilia and colour blindness

Question 29

What is haemophilia?

Answer 29

When blood clots extremely slowly due to the absence of a protein blood clotting factor. It could be fatal.

Question 30

Why is haemophilia sex linked?

Answer 30

If a male inherits the recessive haemophilia allele (on X) they cannot have corresponding dominant allele on Y and so develop haemophilia.

Question 31

Can females suffer from haemophilia?

Answer 31

Yes they can but at a much rarer rate as they can carry the gene but wont suffer from haemophilia if they carry the dominant allele in one of the X chromosomes.

Question 32

What is dihybrid inheritance?

Answer 32

Inheritance of two genes

Question 33

What does dihybrid inheritance show?

Answer 33

The inheritance of two different characteristics, caused by 2 genes, which may be located on different pairs of homologous chromosomes.

Question 34

Whats the monohybrid cross ratio?

Answer 34

3:1

Question 35

Whats the dihybrid cross ratio?

Answer 35

9:3:3:1

Question 36

Whats the codominance cross ratio?

Answer 36

1:2:1

Question 37

Whats the dominant epistasis cross ratio?

Answer 37

12:3:1

Question 38

Whats the recessive epistasis cross ratio?

Answer 38

9:3:4

Question 39

Whats the complimentary epistasis cross ratio?

Answer 39

9:7

Question 40

Why might the ratio of phenotypes better different than expected?

Answer 40

-The fertilisation of gametes is a random process so in a small sample a few chance events can lead to a skewed ratio -The genes being studied are both on same chromosome (linked genes). If no crossing over occurs the alleles for two characteristics will always be inherited together.

Question 41

Whats autosomal linkage?

Answer 41

Genes present on the same, non sex chromosome

Question 42

What are linked genes?

Answer 42

Genes present on the same chromosome

Question 43

What does recombinant mean?

Answer 43

New combination of alleles/DNA from two sources.

Question 44

Whats recombinant frequency equation?

Answer 44

Number of recombinant offspring / total no of offspring

Question 45

What does a recombinant freq of 50% indicate?

Answer 45

No linkage and genes are on separate chromosomes.

Question 46

Wht does a recombinant freq less than 50% indicate?

Answer 46

Is a gene linkage and random process of independent assortment has been hindered.

Question 47

What is chi squared test for?

Answer 47

Statistical test that measures the size of the difference between the results you acc get and those you expected to get

Question 48

What is chi squared test formula?

Answer 48

X^2 = sigma((O-E)^2 /E) X^2 = test stastic Sigma = the sum of O = observed frequencies E = expected frequencies

Question 49

If x^2 is less than critical value what does that mean?

Answer 49

There is no significant difference between expected and observed

Question 50

What does it mean if x^2 is greater than critical value?

Answer 50

There is a significant difference between expected and observed values

Question 51

What is degrees of freedom and how is it calculated?

Answer 51

The number of comparisons being made. n - 1. n = no of categories or possible outcomes present in analysis