Ch13 Reproduction

Question 1

asexual reproduction basics

Answer 1

involves one parent
cells divide by mitosis
no variation in offspring- genetically identical clones

Question 2

sexual reproduction

Answer 2

involves male sex cell and female sex cell
the two gametes fuse to form a zygote
offspring have variation due to mixing of genetic info

Question 3

Formation of gametes

Answer 3

meiosis

Question 4

How does meiosis work

Answer 4

The genetic information of a cell is copied into four sets
Each chromosome forms a pair of chromatids
The cell then divides twice in succession to form 4 gametes
each has a single set of chromosomes(the chromosome number is reduced by half- 23)
Each gamete produced is genetically unique

Question 5

gametes

Answer 5

organism’s reproductive cells

Question 6

Fertilisation

Answer 6

When the two gametes fuse during fertilisation, it restores the normal number of chromosomes
(23+23=46)
The combination of genes in each fertilised egg is unique(variation)
The fertilised egg then divides by mitosis, increasing number of cells rapidly
As embryo develops, the cells differentiate

Question 7

haploid

Answer 7

23 chromosomes within a cell

Question 8

diploid

Answer 8

46 chromosomes within a cell

Question 9

Asexual fungi reproduction

Answer 9

common reproduction is asexual by spores

e.g. toadstools, puffballs and mould

Question 10

Sexual fungi reproduction

Answer 10

when conditions aren’t good to give variation for survival advantage

two hyphae from different fungi join and the nuclei fuse to create new hyphae with two sets of chromosomes
it undergoes meiosis to make haploid spores which are different from original hyphae
spores produce fungi better adapted to survive

Question 11

hyphae

Answer 11

mass of thin threads that make up fungi

Question 12

sexual plant reproduction

Answer 12

the gametes pollen(male) and egg cells(female) are produced using meiosis

Question 13

asexual plant reproduction

Answer 13

e.g. strawberry plants, spider plants and the divisions of bulbs in daffodils

Question 14

asexual malaria parasites reproduction

Answer 14

only happens in human liver and blood cells

Question 15

sexual malaria parasites reproduction

Answer 15

inside mosquito red blood cells
when mosquito takes her blood meal, the drop in temperature between human body and mosquito triggers sexual reproduction in parasites
20 minute window when sexual forms develop and bursts out of blood cells
sexual forms fuse to form zygote with 2 sets of chromosomes(variation)
zygotes undergo meiosis to produce new asexual parasites

Question 16

genome of an organism

Answer 16

the entire genetic material of that
organism
e.g. chromosomes and mitochondria genetic info

Question 17

mitochondria dna

Answer 17

always inherited from the mother(comes form the egg)

Question 18

DNA

Answer 18

long polymer molecule made up of repeating nucleotide units

they twist and spiral to form a double helix

Question 19

nucleotide

Answer 19

common sugar
phosphate group
either 4 different bases attached to the sugar

Question 20

base groups

Answer 20

A with T on the opposite strand

G with C on the opposite strand

Question 21

Nucleotides grouped into 3 bases

Answer 21

sequence of the three bases code for a particular amino acid

order of the bases controls the order in which amino acids are assembled to produce a particular protein

Question 22

Importance of understanding the human genome

Answer 22

search for genes linked to different types of disease
- able to predict risk for each individual

understanding and treatment of inherited disorders
- e.g. cystic fibrosis and sickle cell disease

use in tracing human migration patterns from the past
- understanding human evolution

Question 23

protein synthesis

Answer 23

1. genes in DNA -produce a template for the proteins by reflecting the sequence of bases in the DNA
2. template leaves nucleus through pores in the nuclear membrane and binds to the surface of a ribosome
3. cytoplasm contains carries molecules, each attached to a specific amino acid.
4. The carrier molecules attach themselves to the template in the order given by the DNA
5. the amino acids are joined together to form a certain protein
6. this process occurs until the template is completed
7. protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm
8. protein then folds to create unique shape to carry out it’s job function e.g. structural protein it will form fibrous structures like collagen

Question 24

Gene expression

Answer 24

the process by which specific genes are activated to produce a required protein

Question 25

non-coding parts of DNA

Answer 25

determines how much of gene is switched on or off variation in non-coding parts affect how genes are expressed

Question 26

mutations in coding part of DNA

Answer 26

changes in existing genes - most don't alter protein formed sometimes alters protein formed to give it a different shape e. g. enzyme active site no longer fits substrate e. g. structural protein loses its strength may give an advantage e. g. more efficient enzyme e. g. stronger structural protein

Question 27

mutations in non-coding part of DNA

Answer 27

can affect which genes are switched on or off(expressed) | - have big effect on phenotype

Question 28

allele

Answer 28

different versions of the same gene | each one codes for a different protein

Question 29

gene

Answer 29

small section of DNA on a chromosome | each gene codes for a particular sequence of amino acids, to make a specific protein

Question 30

dominant allele

Answer 30

always expressed in the phenotype even when they are only present in one of the chromosomes

Question 31

recessive allele

Answer 31

only expressed in the phenotype if they are present on both chromosomes(no dominant alleles present)

Question 32

phenotype

Answer 32

the physical appearance or biochemistry of an organism regarding a particular characteristic e.g. black fur or blue eyes

Question 33

genotype

Answer 33

the genetic arrangement(collection of alleles) that determines the traits that an organism inherited from its parents e.g. Bb

Question 34

homozygous

Answer 34

alleles are both identical for the same characteristic AA or aa homozygote- individual who has two identical alleles for a particular gene

Question 35

heterozygous

Answer 35

alleles are both different for the same characteristic Aa heterozygote- individual who has different alleles for a particular gene

Question 36

Cystic fibrosis

Answer 36

``` inherited disorder of cell membranes prevents movement of certain substances from one side to the other mucus becomes thick and sticky organs become clogged caused by recessive allele ```

Question 37

polydactyl

Answer 37

inherited disorder - having extra fingers or toes | caused by dominant allele

Question 38

Embryo screening types

Answer 38

Amniocentesis - taking some fluid from around developing foetus which contains foetal cells Chorionic villus sampling of embryonic cells - taking a sample of tissue from developing placenta

Question 39

Embryo screening disadvantages

Answer 39

1. increase risk of miscarriage(even if foetus is healthy) 2. can give false positive or negatives 3. hard decision for parents- emotional turmoil 4. expensive - everyone should have the tests(costly for society to provide healthcare for child affected by genetic disorder) 5. ethical - could give rise to demand for 'designer babies' 6. no cure