Inheritance, Variation and Evolution Flashcards
Where is DNA found?
In the nucleus in chromosomes
DNA is made of 2 strands coiled together in the shape of…?
A double helix
What’s a gene?
A small section of DNA found on a chromosome
What does it mean that a gene codes for?
Tells the cells to make
Each gene codes for?
A particular sequence of amino acids which make a specific protein
What do genes do?
Tell cells in what order to put amino acids together
What’s a genome?
The entire set of genetic material in an organism
DNA is made up of lots of repeating units called?
Nucleotides
What does each nucleotide consist of?
A sugar, a phosphate group and one base
Each base links to a base on the ________ strand in the helix
Opposite
Which base does base T pair up with?
A
Which base does base C pair up with?
G
What decides the order of amino acids in a protein?
The order of bases in a gene
Each amino acid is coded for by a sequence of how many bases in a gene?
3
Proteins are made on r_____?
Ribosomes
How does the cell get the code (to make proteins) from DNA to ribosome
By mRNA
How’s mRNA made?
By copying the code from DNA
What does mRNA do?
Carries the code between DNA and ribosome
How are the correct amino acids brought to the ribosomes?
By carrier molecules
How many types of amino acids are there?
20
Name 2 examples of proteins
Enzymes
Hormones (e.g. insulin)
What’s a mutation?
A random change in an organisms DNA (gene)
Mutations change the sequence of…?
DNA bases in a gene
What can mutations lead to?
Changes in the protein that bases code for
What does the sequence of DNA bases code for?
The sequence of amino acids (that make up a protein)
How could a mutation affect an enzyme’s function if its shape is changed?
The active site no longer binds to its substrate
What are the 3 different types of mutations?
Insertions, deletions and substitutions
What are insertions?
A new base is inserted into the DNA base sequence where it shouldn’t be
(Every 3 bases codes for an amino acid)
What are deletions?
A random base is deleted from the DNA sequence (can have knock on effects)
What are substitutions?
A random base in the DNA sequence is changed to a different base
How many chromosomes does each gamete contain?
23
(half the number in a normal cell)
Give 2 examples of gametes
Sperm and Egg
Why does the offspring in sexual reproduction contain a mixture of genes
There are two parents
Mixture of genetic information (chromosomes) produces _______ in the offspring
Variation
How many parents are involved in asexual reproduction?
1
How many parents are involved in sexual reproduction
2
By which process does asexual reproduction happen
Mitosis
What happens during mitosis
A cell makes a new cell by dividing in 2
(New cell has exactly the same genetic information as the parent cell)
The offspring in asexual reproduction are genetically _____ to the parent
Identical (they’re clones)
By which process are gametes made?
Meiosis
Describe how cells divide during meiosis
Cell duplicates it’s genetic info, forming 2 armed chromosomes (exact copies) and arrange themselves into pairs
- First division: chromosome pairs line up in centre of the cell
- Cell divides into 2
- The pairs are pulled apart so each new cell has only one copy of each chromosome
- Second division: chromosomes line up in the centre of the cell
- The arms of the chromosomes are pulled apart (why gametes have half number of chromosomes)
- The 2 cells divide again to produce 4 gametes (each genetically different as chromosomes from mother and father get shuffled up)
Why is sexual reproduction better than asexual in terms of variation?
Variation increases the chance of species surviving a change in environment
What are some advantages of asexual reproduction
- Only need to be one parent
- Uses less energy as you don’t have to find a mate
- Faster than sexual
Which organism can reproduce both asexually and sexually
Mosquitos - when it bites a human, it transfers the parasite, which reproduces sexually when in the mosquito and asexually when in the human
How many pairs of chromosomes are in every human body cell
23
What’s the genetic diagram called beginning with P?
Punnett square
All genes exist in different versions called…
Alleles
If an organism has 2 alleles for a particular gene that are the same then it’s …
Homozygous
If an organism has 2 alleles for a particular gene that are different, then it’s …
Heterozygous
The allele for the characteristic that’s shown is the d_______ allele
Dominant
The allele for the characteristic that’s not shown is r_____ allele
Recessive
How does an organism display a recessive characteristic?
Both its alleles must be recessive
How does an organism display a dominant characteristic?
It can either have 1 dominant and 1 recessive allele (Cc) or 2 dominant alleles (CC)
What’s your genotype?
The combination of alleles you have
What’s your phenotype?
The characteristics you have
What happens when you have cystic fibrosis?
Your body produces lots of thick sticky mucus in air passages and pancreas
What is the allele that causes cystic fibrosis?
Recessive allele ‘f’
People with only one copy of ‘f’ allele (cystic fibrosis) won’t have the disorder - they’re known as?
Carriers
How would a child inherit cystic fibrosis from their parents?
Both parents must be either carriers or have the disorder
What’s polydactyl?
A baby is born with extra fingers or toes
By which allele is polydactyl caused?
Dominant allele ‘D’
What did Mendel discover?
Characteristics in plants were passed on from one generation to the next
What plants did Mendel cross for his experimentation?
Pea plants
What were the three conclusions Mendel reached about heredity in plants?
1) Characteristics in plants are determined by hereditary units (alleles)
2) Hereditary units are passed onto offspring unchanged from both parents
3) Hereditary units can be dominant or recessive
What causes genetic variation?
Combining of genes from two parents
What causes environmental variation?
The environment, including conditions that organisms live and grow in
(e.g. plant grown in sun vs shade)
Most characteristics are determined by a mixture of ________ and _________ factors
genetic , environmental
Define evolution
All of todays species have evolved from simple life forms that first started to develop over three billion years ago
Who came up with theory of evolution?
Charles Darwin
Describe the idea of survival of the fittest
Organisms with most suitable characteristics for the environment would be more successful competitors and would be more likely to survive
What does it mean if a species evolves?
Beneficial characteristics become more common and the species changes
What’s speciation?
Over time the phenotype of organisms changes so much due to natural selection that a new species is formed
What are some reasons why species become extinct?
- A new predator kills them
- A new diseases kills them
- Can’t compete with another species for food
Why did so many people not believe in evolution?
It was the first explanation that disproved the existence of God
What was Lamarck’s theory?
If a characteristic was used a lot by an organism, then it would become more developed during its lifetime and the offspring would inherit this characteristic
(E.g. if a rabbit used its legs to escape predators then it’s legs would get longer)
What’s selective breeding?
When humans select plants or animals and breed them together to pass a particular gene to the offspring
What’s the purpose of selective breeding?
- Produce crops with disease resistance
- Improve yields
Describe the process of selective breeding
1) Select organisms which have the characteristics you’re after
2) Breed them with each other
3) Select the best offspring and breed them together
4) Continue this process so desirable trait gets stronger
What’s a problem with selective breeding?
It reduces the gene pool (number of different alleles in a population)
What can happen if gene pool is reduced?
Not much variation so if a new disease appears all of them could be killed
What’s genetic engineering?
Transferring a gene responsible for a desirable characteristic from one organisms genome into another organism, so that it also has the desired characteristic
Describe process of genetic engineering
1) A useful gene is cut from one organisms genome using enzymes and is inserted into a vector
- Vector is usually a virus or bacterial plasmid
2) When vector is introduced to target organism, the useful gene is inserted into its cell
What do scientists use genetic engineering for?
- Treat diabetes - genetically modify bacteria to produce insulin
- Improve size/quality of fruit
- Make plants resistant to disease
What are the 2 types of cloning used to clone plants?
Tissue culture
Plant cuttings
Which type of reproduction are clones made through?
Asexual
Describe the process of tissue culture
1) Part of a plant is cut from a parent plant
2) The plant tissue is placed in a sterile agar growth medium with nutrients and plant hormones
3) It grows into plantlets
4) Plantlets are transferred to be planted in compost
Describe the process of plant cuttings
1) Gardeners take cuttings from good parent plants - new bud is cut off
2) Cuttings are planted and grow into genetically identical versions of the original plant
What are 2 methods to clone animals?
Embryo splitting / transplants
Adult cell cloning
Describe the process of adult cell cloning
1) Take an unfertilised egg and remove its nucleus
2) Take an adult body cell, remove its nucleus and insert the nucleus in the empty egg cell
3) Pass an electric shock through the egg cell to stimulate it
4) The egg starts dividing to form an embryo
5) Insert embryo into an adult female so it develops into a foetus
(It’s genetically identical to the adult body cell donor)
Describe the process of embryo splitting
1) An embryo is made by artificial fertilisation in a lab
2) Split embryo into cells
3) Allow each cell to grow into identical embryos
4) Transfer embryos into host mother and allow them to grow into foetuses
(Cloned offspring are genetically identical to each other)
Describe process of embryo transplants
1) Sperm cells are taken from bull and egg cells from cow
2) The sperm is used to fertilise the egg
3) An embryo develops and is split into cells
4) Cloned embryos are implanted into other cows where they grow into baby calves
What’s an issue with cloning?
Reduces gene pool
What’s a good thing about cloning?
Can help preserve endangered species
What’s speciation?
The development of a new species
How does speciation occur?
When populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring
What are 2 causes of speciation?
Geographical isolation and natural selection
Describe how speciation by isolation occurs
- Land divides due to volcanic activity so species are divided by a barrier and can’t meet to breed
- There’s genetic variation between species as they develop different characteristics to adapt to their environment
- Differences become so great that they won’t be able to breed with one another to provide fertile offspring
- Become separate species
What did Alfred Russel Wallace work on?
Warning colours in animals
(E.g. butterflies to deter predators)
