pg 88-95 of varaition genetic inheritance

Question 1

what are gametes produced by?

Answer 1

meisosis

Question 2

explain the process of meiosis

• to make 4 gametes which are all genetically different

Answer 2

1. DNA duplicates -forms 2 arms
2. arrange themsleves into pairs

3.FIRST DIVISION = chromosome pairs line up in the centre of cell

4. 2 arms pulled apart inot new cells
5. 2nd DIVISION chromosome line up in centre and pulled apart

=have 4 gametes with only a SINGLE SET of chromosomes in it (ALL RANDOM - GET SHIFFLED DURING MEIOSIS

Question 3

what happens when 2 gametes fuse?

Answer 3

the new cell divides by MITOSIS (to make a copy of itself)
-mitosis repeats many times to produce lots of new embryo cells(that develops = see DIFFERENTIATION in SPECIALISED CELLS to mke organism

Question 4

advantages of sexual reproduction?

Answer 4

-produces variation (genes from both parents)

-variation = increases chance of survival they have a SURVIVAL ADVANTAGE

-breed more sucesssfully and pass this gene on = natural selection

-selective breeding
can increse food production = breed anaimals that produce a lot of meat

-

Question 5

advanatges of Asexual reproduction advantages?

Answer 5

-only needs one parent
-less energy = dont have to find a mate
= faster than sexual than sexual reproduction
-produced in favourable conditions

Question 6

name 3 organisms that can reproduce by both methods?

Answer 6

-fungi
-many plant species
-malaria (caused by a parasite - spread by mosquito)

Question 7

how is malaria involve sexual and Asexual reproduction?

Answer 7

-the parasite sexually reproduces when its in the mosquito
-asexually when its in the human

Question 8

how do fungi sexually and Asexually reproduce?

similar to plants

Answer 8

Asexually-produced spores form fungi that is genetically identical to parent

-sexually produce introduce variation = better chance of survival

Question 9

how many pairs of chromosomes are in a human?

Answer 9

23 pairs

Question 10

what do 22 of the pairs do?

Answer 10

control characteristics

Question 11

what does the last pair determine

Answer 11

decide your sex

Question 12

what letter is a male chromosome?

Answer 12

XY
(Y = causes male characteristics)

Question 13

what is the letter for female chromosomes?

Answer 13

XX
combination = allows female characteristics to develop

Question 14

practise drawing punnet squares

Answer 14

xx

Question 15

what does homoxygous mean?

Answer 15

if an organism has 2 ALLELES for a gene that are the SAME

Question 16

what does hetrozygous mean?

Answer 16

if an organism has 2 ALLELES for a gene that are DIFFERENT

Question 17

what are the 2 types of allele

Answer 17

-recessive
-dominant

Question 18

when is the reccesive allele expressed

Answer 18

only when there is 2 reccessive alleles (only recessive)

Question 19

when is a dominant allele expressed

Answer 19

whenever it is present

Question 20

whats a phenotype

Answer 20

the genes characteristic / apperance

Question 21

whats a genotype

Answer 21

the genes/alleles an organism contains

Question 22

practise more punnet squares and finding ratios

Answer 22

xx

Question 23

what allele causes CYSTIC FIBROSIS

Answer 23

reccessive

Question 24

what does cystic fibrosis affect?
(genetic didorder)

Answer 24

-body produces sticky thick mucus in air passages and pancreas

Question 25

what allale cause POLYDACTYLY

Answer 25

dominant

Question 26

how can people carry cystic fibrosis but not have it?

Answer 26

its a recessive allele

Question 27

what does the genetic disorder POLYDACTYLY mean?

Answer 27

- have extra fingers or toes

Question 28

whats IVF?

Answer 28

-embryos feritilised in lab then impanted into the womb

Question 29

whats embryo screening?

Answer 29

-before embryo is implanted = can be scanned for disorders -people may threw away ''bad'' embyos

Question 30

3 reasons whypeople are against embryo screening?

Answer 30

- implies ppl w genetic problems are 'undesirable' {may increase PREJUDICE} - expensive -they can pick the most 'desirbale' one

Question 31

why are people for embryo screening

Answer 31

-helps stop people suffering -laws to stop it goign to far -treating disorders cost govement and tax payers more money

Question 32

what was MENDELS 3 conclusions? for 2 crosses in heights for pea plants.

Answer 32

- characteristics in plants determined by HEREDITARY UNITS - hereditary units can be DOMINANT OR RECESSIVE if smone has both - the dominant will always be expressed - hereditary units a passed unchanged from the parent (one from each parent)

Question 33

what are the 2 cuases of variation?

Answer 33

genetic & enviromental

Question 34

give an example of genetic variation: ~ in humans

Answer 34

-eye colour etc. ~ controlled by genes

Question 35

give an example of enviromental variation: ~ in humans

Answer 35

-tattoos,scars (plant = amount of sunlight effects leaf colour)

Question 36

give an e.g of characteristics due to genes and enviroment?

Answer 36

-skin colour -athletic abilty -height -body weight etc.

Question 37

what are the 2 types of variation?

Answer 37

continous & discontinous

Question 38

whats continous variation? -how is it presented

Answer 38

- shows a range of INTERMEDIATES between 2 extremes - shown in a histogram - mainly controlled by both causes of variation e.g height

Question 39

whats discontinuous variation?

Answer 39

- diff characteristics w no INTERMEDIATES between them - shown on a bar chart - mainly controlled by genes e.g sex/eye colour

Question 40

how was mendels work used as a starting point for many diff scientists?

Answer 40

- late 1800s they came familir w chromosomes (observed cell division) - early 20th centuary realised chromosomes and MENDEL 'units' [genes] acted similar - 1953 structure of DNA was discovered