Patterns of inheritance and variation

Question 1

Environmental can result in contributions in a plant (chlorosis) -

Answer 1

When cells are not producing such amounts of chlorophyll and therefore can make as much food. Happen from environmental reasons for example - Lack of light where plants will turn off there chlorophyll production to conserve resources or even mineral deficiencies - lack of iron or magnesium which is needed as a cofactor by some of the enzymes to make chlorophyll.

Question 2

Animals body mass can be resulted mainly from?

Answer 2

Diet

Question 3

Genotype definition -

Answer 3

Combination of alleles that an organism inherits for their characteristics

Question 4

Phenotype -

Answer 4

The observable characteristics of an organism

Question 5

Dominant allele -

Answer 5

Version of a gene that will be always be expressed if present in an organism

Question 6

Recessive allele -

Answer 6

Only be expressed if two copies are present in an organism, not always tell from observable characteristics.

Question 7

Homozygous -

Answer 7

Two identical alleles for a characteristic for example can be dominant or recessive.

Question 8

Heterozygous -

Answer 8

Have two different alleles for a characteristic.

Question 9

Continuous variation -

Answer 9

A characteristic which can take a value within a range, can be caused by genetic and environmental, controlled by a number of genes = polygenes for example height or weight.

Question 10

Discontinuous variation -

Answer 10

A characteristic that can only appear in specific values. Mostly exists due to genetics for example blood group or pea shape.

Question 11

Codominance -

Answer 11

When two alleles occur for a gene both of which are equally dominant. Therefore both alleles of the gene are expressed in the phenotype of the organism if present.

Question 12

When studying codominance they are represented both with capitals but with little letters next to which represent the dominant characteristic they represent -

Answer 12

w r
E.G C and c

Question 13

Multiple alleles in determining a characteristic -

Answer 13

Some genes have more than two versions where a characteristic is determined by a gene with multiple alleles for example blood group for example I B or I A code in the production of antigens or I0 where there are no antigens produced Io is recessive whereas the others are codominant. Therefore your blood group is determined by this of parental phenotypes E.G IA IA or IA I0 is blood group A.

Question 14

Sex linkage -

Answer 14

Some traits are determined by genes carried on the sex chromosomes this is sex linked, as the y chromosome is smaller there are a number of genes on the x chromosome that males only have one copy meaning a characteristic caused by a recessive allele on the section of the x chromosome and is missing on the y chromosome occurs more frequently in males.

Question 15

Sex linked disease is haemophilia explain who is more likely to suffer.

Answer 15

If a male inherits an allele for haemophilia on their x chromosome they cannot have a corresponding dominant allele on their y chromosome and so develop the condition, so the majority of sufferers are males, females who are heterozygous for the haemophilia coding gene are carriers and do not suffer.

Question 16

Linkage def -

Answer 16

The ratios in dihybrid crosses vary because from those expected this is due to linkage where the genes are located on the same chromosome.

Question 17

Autosomal linkage -

Answer 17

Found on those of the autosomes, these chromosomes cannot undergo the normal random shuffling of alleles in meiosis, shown effectively as a single unit.

Question 18

Recombination frequency is?

Answer 18

Measure for the amount of crossing over that happens in meiosis.

Question 19

Linked genes that are on the same chromosome can cause expected ratios to look different from the observed ratio, these can vary due to what is meiosis?

Answer 19

Crossing-over in prophase 1

Question 20

Different combinations of alleles than their parents is called?

Answer 20

recombinant offspring

Question 21

Chi squared formula and meaning of letters -

Answer 21

X (squared) = Sum off - (O-E) squared divided by E

O = observed frequencies
E = expected frequencies

Question 22

Epigenetics definition -

Answer 22

Interactions of genes at different loci for example gene regulation with regulatory genes controlling structural genes.

Question 23

Expected ratios of autosomal linkage with and without crossing over -

Answer 23

With crossing over = 9.3.3.1

Without = 3.1

Question 24

Epigenetics application -

Answer 24

If 4 enzymes are responsible for a pigment for the colour of a plant, if one these genes is not expressed to produce the enzymes then one step will be missing and it will not have the expected colour.

Question 25

Evolution definition -

Answer 25

Change in inherited characteristics of a group of organisms over time.

Question 26

Factors affecting evolution -

Answer 26

Mutation - leads to genetic variation
Sexual selection - alleles coding for characteristics which improve mating success
Genetic drift - change in allele frequency due to random nature of mutation , this will more likely have a greater impact on in a smaller population rather in much larger populations
Natural selection - where individuals have characteristics that improve the chances of survival and reproductions and passing off offspring.

Question 27

Selection pressures -

Answer 27

Such changes in the environment. Like a disease or new predator

Question 28

Founder effect -

Answer 28

Small populations can arise due to the establishment of new colonies leading to the founder effect and a greater effect of genetic drift.

Question 29

Founder effect characteristics -

Answer 29

Show less populations and smaller gene pools with less genetic variation.

Question 30

Genetic bottleneck -

Answer 30

Large decrease in population size that reduces a gene pool.

Question 31

Evolutionary forces -

Answer 31

Show traits of characteristics of living organisms within populations.

Question 32

Stabilising selection -

Answer 32

Taking the birth weight of babies as examples, average birth weight will make up the most common it results in reduction in the alleles of the extreme and allowing a more norm to follow this is an example of natural selection and survival of the fittest as those with different rates are likely to experience disease or other stuff.

Question 33

Directional selection -

Answer 33

When there is a change in the environment and the norm phenotype is not the most advantageous, the allele frequency shifts towards the extreme phenotypes. Like certain moths who are more camouflaged away from the norm and less likely to be eaten.

Question 34

Disruptive selection -

Answer 34

The extremes are selected for (promoted) and the norm is rejected opposite to stabilising when the norm is positively selected.

Question 35

Speciation definition -

Answer 35

The formation of a new species through the process of evolution.

Question 36

Allopatric speciation -

Answer 36

• Most common
• Happens when some of the group are distant from the other due to a physical or geographical barrier
• There will often be different selection pressures due to a new environment witnessed
• This is seen to result in the founder effect as a form of genetic drift

Question 37

Sympatric speciation -

Answer 37

• Occurs within the population which share the same habitat
• Less frequent than allopatric
• Occurs when two different species and form fertile offspring, the hybrid formed which is a new species
• Different number of chromosomes to a parents and will stop interbreeding with the parent population
• Results in the stopping of gene low and reproductively isolates the hybrid organism.
• Reproductive barriers

Question 38

Populations are genuinely polymorphic which means -

Answer 38

They display more than one distinct phenotype

Question 39

Artificial selection is the same as

Answer 39

selective breeding

Question 40

Artificial selection (selective breeding) -

Answer 40

It is the selection for breeding of plants and animals with desirable characteristics which are selected and interbred. Like natural selection but instead of the environment its on artificial factors. Repeated over many generations resulting in changes in the frequencies of alleles within the population eventually causing speciation.

Question 41

Inbreeding is like incest -

Answer 41

The breeding of closely related individuals.

Question 42

Problems with inbreeding -

Answer 42

• Limits the gene pool therefore decreasing genetic diversity
• This reduces the chances of the population
• Organisms that are related closely and are bred are likely to have the same recessive alleles and many genetic disorders are associated from recessive alleles.

Question 43

Gene banks -

Answer 43

Important genetic resource which is used and store biological samples usually frozen used to increase genetic diversity a form of outbreeding,