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Biology revision > Inheritance and Variation > Flashcards

Inheritance and Variation Flashcards

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1
Q

What is DNA ?

A
  • stands for Deoxyribonucleic acid

Carries the genetic code that determines the characteristics of a living organism

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2
Q

What is a Gene ?

A

A section of DNA that codes for a specific protein

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3
Q

What are chromosomes ?

A

Long threads/strands of DNA

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4
Q

Where are chromosomes found ?

A

In a cell’s nucleus

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5
Q

How many pairs of chromosomes are there in each cell ?

A

23 pairs ( 46 in each cell ) except for gametes

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6
Q

What are the human gametes and how many chromosomes does each gamete contain ?

A

Gametes are sex cells, human gametes are egg and sperm cell

Egg and sperm cell contain 23 chromosomes each

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7
Q

What are the plant gametes ?

A

Pollen and egg cell

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8
Q

What type of cell division makes gametes ?

A

Meiosis

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9
Q

What does sexual reproduction involve ?

A

Fusion of the sperm and egg cell, which forms a zygote

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10
Q

What is a clone ?

A

An organism which is genetically identical to the parent

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11
Q

What are some organisms that reproduce asexually ?

A

Aphids, starfish, potatoes, bacteria, fungi etc

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12
Q

What are the types of cell division in asexual reproduction ?

A

Binary fission ( bacteria),mitosis, budding

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13
Q

What are the advantages of asexual reproduction ?

A

Populations can increase rapidly

Saves time and energy finding a mate

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14
Q

What are the disadvantages of asexual reproduction ?

A
  • Very difficult to adapt to a changing environment due to no variation
  • Same traits means same vulnerabilities so if one organism is affected by something, they all will be
    ie disease
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15
Q

Exam Q

Explain why offspring of organisms that reproduce asexually are identical to their parents but the offspring of organisms that reproduce sexually are not

A
  • Asexual reproduction doesn’t involve fertilisation of gametes so there is no mixing of genetic material
  • Organisms produced with asexual reproduction are clones
  • Sexual reproduction involved two gametes which fuse together during fertilisation
  • Fertilised egg contains the genetic information from both parents
  • Mixing of genetic information leads to genetic variation in the offspring
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16
Q

What are some examples of inherited traits ?

A 
Eye colour
Blood type
disabilities
disease
bone structure
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17
Q

what are some examples of environmental traits ?

A

Scars
Piercings
Tattoos
Language and accent

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18
Q

What are some examples of both inherited and environmental traits ?

A 
Height
weight 
skin 
eye sight
hair colour 
personality
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19
Q

What are environmental traits ?

A

Characteristics that can be affected by factors such as diet. climate, culture and lifestyle ( environmental factors)

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20
Q

What are inherited traits ?

A

Characteristics that are passed on to organism by genes

21
Q

Why do farmers use selective breeding ?

A

To ensure they get the characteristics of animals and plants that they want

22
Q

What is selective breeding ?

A

Breeding for desirable genetic traits

23
Q

What are the steps for selective breeding ?

A
  • choose the characteristics
  • choose a male and female from a mixed population, which show the desired traits
  • breed them together
  • pick the best offspring that show the desired characteristics and have them breed
  • repeat until the whole population shows the desired characteristics
24
Q

What are the benefits of selective breeding ?

A

New varieties may be economically important, by producing more or better quality food

Animals can be selected that cannot cause harm ie cattle without horns

25
Q

What are the disdvantages of selective breeding ?

A

Takes a long time

Reduced variation/gene pool means organisms that have same vulnerabilities

rare disease genes can be unknowingly selected as part of a positive trait, leading to problems with specific organisms

can create physical problems in specific organisms, eg large dogs can have faulty hips due to not being formed correctly

26
Q

Why would a farmer want to breed chickens that grow fast ?

A

they would produce eggs more quickly as they would reach maturity faster and have their periods earlier

27
Q

What is discrete/discontinuous data ?

A

Data that can only take certain values

ie rolling a die, values can either be 1,2,3,4,5,6

28
Q

What is continuous data ?

A

Can take any value ( within a range)

ie a person’s height: can be any value ( within a range of human heights) not just fixed heights

29
Q

What are some examples of desired characteristics ?

A
  • Insect resistance in food and crops
  • animals which produce more meat or milk
  • domestic dogs with a gentle nature
30
Q

Why is variation useful in a population ?

A

Allows population to deal with changes in their environment more easily ie new disease, new predator

31
Q

What can interbreeding lead too…

A

Increasing risk of genetic disorders caused by recessive genes.

32
Q

What does genetic engineering involve ?

A

Modifying the genome of an organism by transferring a desirable gene from another organism - results in desired characteristic

33
Q

What is the donor organism in genetic engineering ?

A

Organism the gene is removed from

34
Q

What are restriction enzymes used for in genetic engineering ?

A

Used to cut out a section of DNA from the genome of an organism

35
Q

What are plasmids ?

A

Small, circular strands of DNA

36
Q

Why do we use bacteria to produce human insulin ?

A

Reproduce quickly and asexually, meaning the offspring are all clones. Allows us to produce a lot of human insulin in a short time parameter.

37
Q

What are the steps for producing insulin from bacteria ?

A

1) Take human cell containing the normal insulin gene
2) Insulin gene is cut out of the human genome using restriction enzymes
3) Take the bacterial cell containing the plasmid
4) Plasmid taken out of bacteria and it is cut using restriction enzymes
5) Human Insulin gene is inserted into the bacterium’s plasmid and plasmid is inserted back into the bacteria cell
6) Bacteria cell divides to produce copies of itself which all contain the human insulin gene.

38
Q

What are the advantages of genetic engineering ?

A
  • GM crops let us produce more crops which can solve issues such as global hunger
  • GM crops grow resistant to disease and insects and harsh climates
  • GM crops can save farmers’ money
  • GM crops can have higher nutritional value
39
Q

What are the disadvantages of genetic engineering ?

A
  • can lead to the transfer of allergies
  • Can alter our human digestive system which can be life threatening
  • No information about the long term consequences of eating/producing GM crops
40
Q

How are identical twins created ?

A

Egg and sperm cell fuse together to form a zygote

Zygote divides into a ball of cells ( blastocyst)

Blastocyst splits into two and each ball of cells grows into an embryo

DNA is therefore identical

41
Q

How are non identical twins created ?

A

Two eggs are released during ovulation

Each egg is fertilised by a separate sperm cell

DNA is therefore not identical

42
Q

What are the steps for cloning a plant by cuttings ?

A

1) cut off a branch from the parent plant
2) remove the lower leaves and dip the end of the stem in hormone rooting powder
3) Plant the stem in damp compost
4) Cover the cutting in a clear plastic bag to keep it moist and warm

43
Q

What does hormone rooting powder do ?

A

Contains plant hormones which encourage new roots to grow

44
Q

How can you use tissue culture to clone a plant ?

A
  • Take explants ( small pieces taken from a plant) from the parent plant
  • Transfer explants to plates containing sterile agar jelly
  • Add hormones to trigger the plant cells to divide
  • cells grow to form plant tissue
  • Add more plant hormones to stimulate growth of roots and stems
  • When explants have developed into tiny plantlets transfer them to potting trays, where they will develop into plants.
45
Q

How can you use embryo transplants to clone animals ?

A
  • Start with sperm and egg cell from a male and female horse with desired characteristics
  • Sperm fertilises egg cell forming a zygote
  • We allow zygote develops into an early stage embryo ( cells haven’t yet started to specialise )
  • Glass rod is used to split embryo into two, forming two embryos
  • Two embryos are transplanted into host mothers to grow and develop
  • When the offspring are born they will be identical, (clones)
46
Q

What is the main problem with embryo transplants ?

A

No certainty that the offspring will display the desired characteristics. Can be overcome using adult cell cloning ( nuclear transfer)

47
Q

What are the steps for adult cell cloning ?

A

1) We start off with sheep A and sheep B
2) We take a body cell from sheep A and remove the nucleus
3) We then take an egg cell from sheep B and discard the nucleus
4) The nucleus from sheep A is inserted into the egg cell from sheep B
5) An electric shock stimulates the egg cell to divide to form an embryo
6) When embryo develops into a ball of cells, it is inserted into the womb of an adult female.
7) The lamb born will be a clone of sheep A

48
Q

What is the benefit of adult cell cloning ?

A

Because we are cloning from an adult, we know the characteristics the clone will have

Biology revision (6 decks)

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