B14 - Variation and Evalution

Question 1

what is variation

Answer 1

the difference in phenotypes of individuals of the same species

Question 2

what is variation caused by

Answer 2

• genetics (nature)
• enviroment (nurture)

Question 3

what is natural selection

Answer 3

a process where organisms that are better adapted to an environment will survive and reproduce

1. Within any population there will be a wide variation of alleles
2. In a certain enviroment one phenotype will be more favourable than others, the best adapted indiviuals
3. these individuals are more likely to survive longer
4. those that survive can breed and pass on their allelels to the next generation
5. over many generations the numbers of individuals with favourable phenotypes will increase at the expense of others

Question 4

what is selective breeding

Answer 4

• same as artificial selection
• used in animals and plants

method:
- the desired characteristsics are identified
- they are bred together
- only the offspring exhibiting the desired charcteristics are bred
- this is repeated overl several generations until the desired trait is fully developed

Question 5

what is an alleles

Answer 5

a form of the same gene

Question 6

what is a recessive allele

Answer 6

only expressed when there is no dominant allele or there are two recessive alleles

Question 7

what is a gene

Answer 7

a section of DNA thats codes for a protein, some charcteristics are controlled by a single gene

Question 8

what is a dominant allele

Answer 8

this allele is always expressed in the phenotype when pressent, it is usually presented by a cpaital letter e.g A

Question 9

what is homozygous

Answer 9

a person is homozygous for a gene if they have two of the same alleles e.g AA or aa

Question 10

what is heterozygous

Answer 10

a person is heterozygous for a gene if they have two differemt alleles e.g Aa

Question 11

what is a genotype

Answer 11

the combination of alleles that a person has for a given gene e.g AA, Aa or aa

Question 12

what is a phenotype

Answer 12

the physical appearance of an organism (what characteristic appears)

Question 13

what is embryo screening

Answer 13

Embryonic screening can take place in order to test for alleles

• once cells collected from embryo or fetus they are screened
• DNA is isolated from the embryo cells and tested for spersific disorders

Question 14

what is the chorionic villus sampling - transabdominal method

Answer 14

A needle is inserted through your skin into the womb and guided to the placenta using the image on the ultrasound scan.

Question 15

what is amniocentesis

Answer 15

Amniocentesis is a test you may be offered during pregnancy to check if your baby has a genetic or chromosomal condition, such as Down’s syndrome, Edwards’ syndrome or Patau’s syndrome

Question 16

what is genetic engineering

Answer 16

modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

Question 17

method of genetic enginerring

Answer 17

1. use enzymes to cut at the desired gene
2. insert gene into host organism (uses enzymes to stack DNA together)
3. gene will be expressed in organism