Patterns of inheritance and variation Flashcards Preview

Paper 2 Biological diversity > Patterns of inheritance and variation > Flashcards

Flashcards in Patterns of inheritance and variation Deck (22)
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1

Chlorosis

Condition in which plat leaves look pale/yellow. This is due to environmental factors such as lack of light, mineral deficiency (eg: Mg), virus infections

2

Continuous variation

Characteristic that can take any value within a range, cause by both genetic and environmental factors.
Polygenes
eg: skin colour, leaf surface area

3

Discontinuous variation

Characteristic that can only appear in specific discrete values.
Monogenes or digenes
eg: blood group, albinism

4

Codominance

When 2 different alleles occur for a gene, both equally dominant. This results in both alleles expressed in the organism's phenotype.

5

Genes with multiple alleles

eg: immunoglobulin codes for the production of 3 different antigens: iA, iB, i0 (iA and iB are codominant, while i0 is recessive)

6

Determining sex

Determined by the 23rd pair of chromosomes, as the 22 first pairs are identical.
Female = XX
Male = XY

7

Sex linkage

Characteristics determined by genes on the sex chromosomes - genes are said to be sex linked. There are some characteristics on the X chromosome that male only have one copy of, therefore they can't be expressed if they're recessive.
(eg haemophilia)

8

Dihybrid crosses

Used to show the inheritance of two different characteristics caused by 2 genes, which can be located on different pairs of homologous chromosomes

9

Linkage

The reason why the ratios observed in many dihybrid crosses differ significantly from those expected. The genes are located on the same chromosome = linkage.
Linked genes are inherited as one unit as there is no independent assortment unless they're separated by the chiasmata.

10

Autosomal linkage

When the genes that are linked are found on any other chromosome other than the sex chromosome.

11

Recombination frequency

number of recombinant offspring/total number of offspring

12

Recombinant offspring

They have different combinations of allele than either parent. The closer the genes are in terms of locus, the less likely they are to be separated during crossing over and independent assortment.

13

Chi-squared test

Statistical test used to measure the size of difference b/n the observed results and the expected results.

14

Epistasis

Interaction of genes at different loci. (eg: gene regulation)

15

Types of epistasis

Dominant (dominant allele results in a gene having an effect on another gene)
Recessive (2 recessive alleles lead to a change in action eg enzyme action)

16

Hardy-Weinberg principle

In a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next if there will be no evolution.

17

Hardy-Weinberg formula

p^2+2pq+q^2=1
p^2 = freq of homozygous dominant genotype
2pq = freq of heterozygous genotype
q^2 = freq of homozygous recessive genotype

18

Types of selections

Stabilising
Directional
Disruptive

19

Speciation

Formation of new species through the process of evolution.

20

Allopatric speciation

When some members of a population are separated from the rest by a physical barrier such as a river (geographical isolation)

21

Sympatric speciation

Within populations that share the same habitat, when members of two different species interbreed and form infertile offspring.

22

Artificial selection/Selective breeding

The selection is made in order to perform selective breeding, and produce desired characteristics.