Inheritance and Variation Flashcards
What is DNA ?
- stands for Deoxyribonucleic acid
Carries the genetic code that determines the characteristics of a living organism
What is a Gene ?
A section of DNA that codes for a specific protein
What are chromosomes ?
Long threads/strands of DNA
Where are chromosomes found ?
In a cell’s nucleus
How many pairs of chromosomes are there in each cell ?
23 pairs ( 46 in each cell ) except for gametes
What are the human gametes and how many chromosomes does each gamete contain ?
Gametes are sex cells, human gametes are egg and sperm cell
Egg and sperm cell contain 23 chromosomes each
What are the plant gametes ?
Pollen and egg cell
What type of cell division makes gametes ?
Meiosis
What does sexual reproduction involve ?
Fusion of the sperm and egg cell, which forms a zygote
What is a clone ?
An organism which is genetically identical to the parent
What are some organisms that reproduce asexually ?
Aphids, starfish, potatoes, bacteria, fungi etc
What are the types of cell division in asexual reproduction ?
Binary fission ( bacteria),mitosis, budding
What are the advantages of asexual reproduction ?
Populations can increase rapidly
Saves time and energy finding a mate
What are the disadvantages of asexual reproduction ?
- 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
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
- 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
What are some examples of inherited traits ?
Eye colour Blood type disabilities disease bone structure
what are some examples of environmental traits ?
Scars
Piercings
Tattoos
Language and accent
What are some examples of both inherited and environmental traits ?
Height weight skin eye sight hair colour personality
What are environmental traits ?
Characteristics that can be affected by factors such as diet. climate, culture and lifestyle ( environmental factors)
What are inherited traits ?
Characteristics that are passed on to organism by genes
Why do farmers use selective breeding ?
To ensure they get the characteristics of animals and plants that they want
What is selective breeding ?
Breeding for desirable genetic traits
What are the steps for selective breeding ?
- 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
What are the benefits of selective breeding ?
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
What are the disdvantages of selective breeding ?
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
Why would a farmer want to breed chickens that grow fast ?
they would produce eggs more quickly as they would reach maturity faster and have their periods earlier
What is discrete/discontinuous data ?
Data that can only take certain values
ie rolling a die, values can either be 1,2,3,4,5,6
What is continuous data ?
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
What are some examples of desired characteristics ?
- Insect resistance in food and crops
- animals which produce more meat or milk
- domestic dogs with a gentle nature
Why is variation useful in a population ?
Allows population to deal with changes in their environment more easily ie new disease, new predator
What can interbreeding lead too…
Increasing risk of genetic disorders caused by recessive genes.
What does genetic engineering involve ?
Modifying the genome of an organism by transferring a desirable gene from another organism - results in desired characteristic
What is the donor organism in genetic engineering ?
Organism the gene is removed from
What are restriction enzymes used for in genetic engineering ?
Used to cut out a section of DNA from the genome of an organism
What are plasmids ?
Small, circular strands of DNA
Why do we use bacteria to produce human insulin ?
Reproduce quickly and asexually, meaning the offspring are all clones. Allows us to produce a lot of human insulin in a short time parameter.
What are the steps for producing insulin from bacteria ?
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.
What are the advantages of genetic engineering ?
- 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
What are the disadvantages of genetic engineering ?
- 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
How are identical twins created ?
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
How are non identical twins created ?
Two eggs are released during ovulation
Each egg is fertilised by a separate sperm cell
DNA is therefore not identical
What are the steps for cloning a plant by cuttings ?
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
What does hormone rooting powder do ?
Contains plant hormones which encourage new roots to grow
How can you use tissue culture to clone a plant ?
- 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.
How can you use embryo transplants to clone animals ?
- 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)
What is the main problem with embryo transplants ?
No certainty that the offspring will display the desired characteristics. Can be overcome using adult cell cloning ( nuclear transfer)
What are the steps for adult cell cloning ?
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
What is the benefit of adult cell cloning ?
Because we are cloning from an adult, we know the characteristics the clone will have
