patterns of variation

Question 1

what are the two types of variation?

Answer 1

continuous and discontinuous

Question 2

whats continuous variation ?

Answer 2

when individuals in a population vary within a range - there are no distinct characterstics eg height , waist size. influenced by many genes.

Question 3

whats discontinuous variation?

Answer 3

where there are two or more distinct characteristics and each individual falls into only one.and there are no intermediates. eg blood groups . usually influenced by only one gene.

Question 4

what are the different factors variation can be influenced by ?

Answer 4

• enviormental
• genes
• both

Question 5

how can variation be influenced by the genes ?

Answer 5

• different individuals have different genes
• individuals of same species have same genes but different versions of them - allele
• the genes and alleles of an organism that makes its genotype
• sexual reproduction leads to variation in genotypes within a species. meiosis makes gametes with a unique assortment of alleles through crossing over and indepenedent assortmentbof chromosomes. also the random fusion of gametes during fertilisation, increases the genetic variation of an offspring.
• Also the difference in genotype result in variation in phenotype - the characterstics displayed by an organism - variation in a phenotype is known as phenotypic variation
• inhertited characterstics that show continuous variation ae usually influenced by many genes and these characterstics is known as polygenic characterstics eg human skin colour - it comes in a lot of different shades.
• inherited characterstics that show discontinuous variation is usually influenced by only one gene . characterstics are only controlled by one gene and this is known as monogenic eg violet colour - it can either be coloured or white.

Question 6

allele

Answer 6

-different version of a gene

Question 7

gene

Answer 7

a sequences of bases of dna that codes for a protein

Question 8

genotype

Answer 8

the alleles an organism has eg bb ,Bb

Question 9

phenotype

Answer 9

the characterstics that those alleles produce

Question 10

Dominant

Answer 10

An allele whose characterstics appear on the phenotype even if only one of its copy is present

Question 11

recessive

Answer 11

an allele whose characterstics appear on the phenotype if two copies are present its shown by bb - lower case

Question 12

co dominant

Answer 12

alleles that are both expressed in the phenotype - neither one is recessive

Question 13

locus

Answer 13

the fixed position of a gene on a chromosome. alleles of a gene are found at the same locus on each chromosome in a pair.

Question 14

homozygote

Answer 14

an organism that carries two copies of the same allele eg: BB OR bb

Question 15

heterozygote

Answer 15

an organism that carries two different alleles eg Bb

Question 16

carrier

Answer 16

a person carrying the allele which is not expressed in the phenotype but can be passed on to the offspring

Question 17

how can variation be influenced by the enviorment ?

Answer 17

it can be caused by difference in the environment eg climate ,food, lifestyle. characterstics controlled by the environment change over time eg : etiolation - this is when plants grow abnormally long and spindly inorder to reach the sunlight.

• also chloroisis - this is when plants don’t produce enough chloroplyll and turn yellow. its caused by several enviormental factors such as lack of magnesium in the soil.

Question 18

how can variation be influenced by both enviorment and genes?

Answer 18

genetic factors determine genotype and the characterstics an organism is born with , but enviormental factors can influence how some characterstics develop. most phenotypic variation is caused by the combination of genotype and the enviormental factors. phenotypic variation influenced by both is usually shown by continuous variation
eg pea plants - come in tall and dwarf forms which is determined by its genotype however, the exact height of all plants and dwarfs varies because of the enviormental factors eg light and water avalibility.

Question 19

what are the possible ways to show possible genotypes of an offspring / ?

Answer 19

genetic diagram and punnett square