B6 inheritance, variation and evolution

Question 1

What is sexual reproduction?

Answer 1

joining of male and female gametes (in fertilization)

Question 2

What is asexual reproduction?

Answer 2

involves one parent and no joining of gametes

Question 3

What are the sex cells found in plants?

Answer 3

pollen and egg cells

Question 4

What are the sex cells found in animals?

Answer 4

sperm and egg cells

Question 5

How are gametes formed?

Answer 5

Through meiosis.

Question 6

What is meiosis?

Answer 6

Formation of four non-identical cells from one cell.

The cell makes copies of its chromosomes.
Then divides into two cells with half no. of chromosomes.
Then divides again with a 1/4 of total no. of chromosomes.

Question 7

What are some advantages of sexual reproduction? (2)

Answer 7

-variation in offspring
(more likely to survive if the environment changes)
-allows the use of selective breeding

Question 8

What are some advantages of Asexual reproduction? (4)

Answer 8

• only one parent needed
• uses less energy
• faster (no mate needed)
• lots of offspring can be produced

Question 9

What organisms use both types of reproduction?

Answer 9

-malarial parasite
(asexually in MOSQUITO, sexually in the human host)
-some fungi
(spores produced asexually, or sexually when conditions change)
-some plants
(asexually, runners or bulbs
sexually, pollen)

Question 10

Define gene

Answer 10

A short section of DNA.

Question 11

Define genome

Answer 11

All of the genetic information in an organism

Question 12

Why is understanding the human genome useful?

Answer 12

Improved treatment of inherited disorders

Helped to trace past humans migration patterns

Question 13

What are the complementary base pairings?

Answer 13

A T

G C

Question 14

How do bases code for proteins?

Answer 14

The order of the bases forms codes. Each group of three bases code for an amino acid. Amino acids join to form a protein.
The order and type of amino acid determine the protein.

Question 15

How are proteins synthesised?

Answer 15

• the two strands of DNA are pulled apart
• mRNA nucleotides match to their complementary bases
• mRNA nucleotides are joined together, creating a new strand which is a template of the original DNA
• the mRNA moves out of the nucleus onto the RIBOSOMES
• the bases are read, in 3s to code for an amino acid, from the mRNA.
• the corresponding amino acids are brought to the ribosomes by carrier molecules.
• the amino acids connect together to form a protein with a unique 3D shape.

Question 16

What are 3 examples of proteins?

Answer 16

Enzymes- biological catalysts
Hormones- chemical messengers that send messages around the body
Structural protein- strong protein to form structures

Question 17

What can mutations do?

Answer 17

they change the sequences of bases in DNA by inserting, deleting or substituting a base from the code.
They occur continuously but most do not alter the protien

Question 18

Does all of the DNA code for proteins?

Answer 18

no. non-coding parts can switch genes on and off

variations in these areas of DNA may affect how genes are expressed

Question 19

What is the difference between genotype and phenotype?

Answer 19

Genotype is the combination of alleles

Phenotype, however, is the physical characteristic observed.

Question 20

Heterozygous vs Homozygous

Answer 20

homo = aa or AA

hetero=Aa

Question 21

is Polydactyly caused a dominant or recessive allele?

Answer 21

Dominant.

extra fingers/toes

Question 22

What type of allele is Cystic fibrosis caused by?

Answer 22

recessive.

thick mucus in airways and pancreas

Question 23

How many PAIRs of chromosomes do humans have?

Answer 23

23 pairs

46 chromosomes

Question 24

What is variation?

Answer 24

Differences in characteristics of individuals in a population

Question 25

What can cause variation?

Answer 25

• genes (meiosis)
• environment (conditions organism grows up in)
• both

Question 26

How does evolution occur through natural selection?

Answer 26

mutations occur providing variation.
if a mutation provides a survival advantage the organism is more likely to survive to breeding age.
the mutation may then be passed down to their offspring. overtime, the frequency of mutation will increase.

Question 27

What is selective breeding?

Answer 27

When humans choose which organisms to breed to produce a certain, desirable characteristic

Question 28

What are some examples of selective breeding?

Answer 28

• disease-resistant plants
• meaty cows
• fast horses/greyhounds

Question 29

What is a potential issue with selective breeding?

Answer 29

inbreeding meaning the gene pool is reduced and, if there is an environmental change or disease, they have a low survival rate.
also, a greater chance of genetic defects being present.

Question 30

What is genetic engineering?

Answer 30

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

Question 31

How does genetic engineering work?

Answer 31

• genes from chromosome are cut out using restrictive enzymes.
• a virus or plasmid is cut using the same enzyme.
• the loop and gene ends are joined together by DNA ligase enzymes

Question 32

Examples of genetic engineering?

Answer 32

crops (resistant to insects)

medicine (cure inherited disorders)

Question 33

Concerns of GM crops?

Answer 33

• infertile –> lead to infertility in other species
• reduce biodiversity
• don’t fully understand the risks to humans

Question 34

tissue culture vs cuttings

Answer 34

TC
plants cells are taken -> placed in growth medium -> grow into new plants-> genetically identical to parent
CUTTINGS
section of the stem is taken from the plant (with characteristic)–> planted and produce clones genetically identical to the parent

Question 35

embryo transplant

Answer 35

sperm and egg cells with characteristics obtained –> fertilised in lab –> embryo divides and is inserted int host mother –> offspring is genetically identical

Question 36

adult cell cloning

Answer 36

nucleus removed from unfertilised egg cell –> nucleus removed from adult body cell and placed in denucleated egg cell –> electric shock -> egg cell divides to form embryo -> planted into the womb of human –> offspring is the clone of an adult body cell