B13: Reproduction

Question 1

what is

sexual reproduction?

Answer 1

• fusion of 2 gametes
• formation of gametes involves MEIOSIS

Question 2

what is

asexual reproduction

Answer 2

-ony one parent reuqired so NO FUSION OF GAMETES
-offspring are genetically identical to parents/eachother (clones)
- uses MITOSIS

Question 3

PROCESS OF MEIOSIS?

Answer 3

1) each chomosome is DUPLICATED, forming X chromosomes
2)first division:chromosome pairs line up along centre of cell/pulled apart so each new cell has one copy of each chromosome
3)second division: chromosome lines up in centre of cell/arms of chromosomes pulled apart
4) 4 haploid daughter cells produced - have half the genetic material of parent cell

Question 4

importance of meiosis ?

Answer 4

produces gametes
inreases genetic variation in offpspring

Question 5

AD AND DIS OF SEXUAL REPRODUCTION?

Answer 5

AD : increase genetic variation
- the species can adapt to new environemnts bc variation
- disease less likely bc of variation

DIS : takes time and energy to find mates
- difficult for isolated species to reproduce

Question 6

AD and DIS of asexual reproduction?

Answer 6

ad: - Population can be increased rapidly
- more time and energy efficient
- faster than sexual reproduction

DIS : - no genetic variation
- vulnerable to chnages in eviron
- disease is likely to affect

Question 7

what ORGANISMS use both types of reproduction and how ?

Answer 7

MALARIAL PARASITES : asexually in human host, sexually in mosquito
FUNGI : spores are produced both ways
PLANTS : seeds are produced either way

Question 8

what is the genome?

Answer 8

entire set of genetic material of an organism is a GENOME

Question 9

what is a gene?

Answer 9

short length of DNA found on chromosome
- each gene codes for particular sequnce of amino acids

Question 10

why is the HUMAN GENOME PROJECT an important breakthrough?

Answer 10

• helps find treatemnts for genetic disorders
• can undertant human migration patterns from past

Question 11

what are NUCLEOTIDES? and what do they consist of ?

Answer 11

induvidual subunits of DNA
- CONSISTS OF : -sugar and phsophate groups
- one of the four bases attached to phosphate

Question 12

what codes for amino acids ?

Answer 12

a sequence of 3 bases is code for PARTICULAR AMINO ACID
-order of bases controls order/different types of amino acids

Question 13

Function of ribosomes?

Answer 13

ribosomes ‘read’ code on the mRNA in groups of 3
- base code is transcibed onto an RNA molecule called messenger RNA (mRNA)
- mRNA can move out nucleus and attached to ribosome
- carrier molecules bring specific amino acids to add to growing protein chain
- ribosome translates sequence of bases into sequence of amino acids
- once amino acids have been assembled, relased from ribosome to fold/form a protein

Question 14

proteins function?

Answer 14

ENZYMES
HORMONES
STRUCTURAL PROTEINS - provide structure/strong (eg collagen)

Question 15

what are mutations?

Answer 15

random changes that occur in the sequence of DNA bases in a gene/chromosome
- can sometime slead to chnage in protein (as dna bases are changed)

Question 16

types of mutations?

Answer 16

INSERTIONS : - new base inserted into DNA sequence
- changes amino acid that would have been coded for by the 3 bases
- can change the groups of 3 bases further in the DNA sequence

DELETIONS : - base is randomly deleted from DNA sequence
- changes amino aicd that would have been made
- changes group of 3 bases aswell

SUBSTITUTIONS: - base is randomly swapped for a different base
- only changes the group of 3 bases in which the MUTATION OCCURS (not further in the DNA sequence)

Question 17

effects of mutations?

Answer 17

only small no. mutations code for significantly altered protein with differerent shape –> affect ability to perform funtion ( active site can change/lose strength)

Question 18

what happens if mutation occurs in non-coding DNA ?

Answer 18

the expression of genes are altered/ may not be expressed at all

Question 19

define

allele and the 2 types?

Answer 19

different verison of a particular gene
DOMINANT: always expressed
RECESSIVE : only expressed if two copies present

Question 20

difference between GENOTYPE AND PHENOTYPE?

Answer 20

GENOTYPE: combination of alleles that control each charcteristic
PHENOTYPE: observable characteristics of an organism

Question 21

what is Polydactyly and the cause?

Answer 21

havinge extra fingers/toes
- caused by DOMINANT ALLELE

Question 22

What is CYSTIC FIBROSIS and cause?

Answer 22

• disorder of cell membranes , resulting in thick mucus in airways and pancreas
• RECESSIVE ALLELE - both parents have to be carriers , or one has CF /the other is a carrier

Question 23

arguments for embryonic screening?

Answer 23

• reduce no. ppl suffering
• treatement is expensive
• many regulation to stop it form getting out of hand

Question 24

arguments againts embryonic screening?

Answer 24

• could encourage DESIGNER BABIES
• expensive
• promote prejudice - those iwth disorder cant live as long/unwanted
• decision to terminate pregnancy need to made
• can lead to miscarrage

Question 25

whch pair of chromosmes carry sex determining genes/ what do females and males carry?

Answer 25

23rd
FEMALE : XX
MALE : XY

Question 26

what is embryonic screening?

Answer 26

IVF is where embryos fertilised in lab /implanted into mom’s womb
- cell taken from embryo to analyse genes before implanting
- detects for genetic disorders