Inheritance,Variation and Evolution. Flashcards
What is DNA?
Deoxyribonnucleic Acid.
Chemical that all of the genetic material in a cell is made up from.
What does DNA contain?
Coded information, all the information to put an organism together to make it function.
What does your DNA determine?
What inherited characteristics you have.
What proteins the cell produces eg:haemoglobin and keratin. That in turn determines what type of cell it is eg:red blood cell and skin cell etc
Where is DNA found?
Nucleus of animals and plant cells in really long structures called chromosomes.
What do chromosomes come in?
Pairs.
What is DNA made up of?
It is a polymer.
Made up of two strands, coiled together in the shape of a double helix.
Define gene.
Small section of DNA found on a chromosome.
What does each gene code for?
A particular sequence of amino acids which are put together to make a specific protein.
How many amino acids are used to make up thousands of different proteins?
20
What is the job of a gene?
Tells cells in what order to put the amino acids together
Define Genome.
Term for the entire set of genetic material in an organism.
What have scientists worked out?
about the genome?
The complete human genome.
Understanding the human genome is a really important tool for science and medicine for many reasons.
What does understanding of the genome allow scientists to do?
To identify genes in the genome that are linked to different types of disease.
Knowing which genes are linked to inherited disease could help us understand them better and develop effective treatments.
Science look at genome to trace migration of certain populations of people around the world.
All modern humans descended from common ancestor who lived in Africa, but humans are found all over the planet.
Human genome is identical in all humans but as different populations of people migrated from Africa they gradually develop tiny differences in their genomes.
By investigating these differences, scientists can work out when new populations split off in a different direction and what route they took.
What are DNA strands made from?
They are polymers, made up of lots of repeating units called nucleotides.
What does each nucleotide consist of?
One sugar molecule, one phosphate molecule and one “base”
What do the sugar and phosphate molecules in the nucleotides form?
A backbone, to the DNA strands.
The sugar and phosphate molecules alternate.
One of four different bases -A,T,C or G- joins to each sugar.
What does each base link up to?
A base on the opposite strand in the helix.
Which bases pair up with each other?
A pairs up with T
C pairs up with G
This is called complimentary base pairing.
What is complimentary base pairing.
Order of bases in a gene that decides the order of amino acids in a protein.
What is each amino acid coded for?
By a sequence of three bases in a gene.?
Amino acids join together to make what?
Various proteins, depending on the order of the genes bases.
What controls whether a gene is expressed or not.
Parts of a DNA that does not code for proteins, some of these non coding parts switch genes off so they control whether the gene is expressed. (used to make a protein)
Where are proteins made?
In the cell cytoplasm on tiny structures called ribosmomes.
To make proteins what do ribosomes do?
They use the code in the DNA. DNA is found in the nucleus and can’t move out of it as it is really big. So the cell needs to get the code from the DNA to ribosomes.
This is done using mmolecule mRNA which is made by copying the code from DNA.
The mRNA acts as a messenger between DNA and ribosome. It carries the code between two.
The corect amino acids are brought to ribosomes in the correct order by carrier molecules.
What allows the protein to perform the task it is meant to do?
When a chain of amino acids has been assembled it fold into a unique shape which allows it to perform the task it is meant to.
Give examples of different types of proteins.
Enzymes,hormones and strucutral proteins.
Define enzymes.
Act as a biological catalyst to speed up chemical reactions in the body.
Define hormones.
Used to carry messengers around the body. EG: Insulin is a hormone released into the blood by the pancreas to regulate the blood sugar level.
Define structural proteins.
Are physically strong. EG: collagen is a structural protein that strengthens connective tissues like ligaments and cartilage.
Define mutations.
Changes to genetic code, occasionly a gene may mutate.
A mutation is a random change in an organsisms DNA they can sometimes be inherited.
When do mutatations occur?
Continuosly and spontaneously. Eg: when a chromosome isn’t replicated properly however the chance of mutation is increased by exposure to certain substances or some types of radiation.
What does a mutation change?
Sequence of DNA bases in a gene which produces a genetic variant. As the sequence of DNA bases codes for sequence of amino acids that make a protein mutations to a gene lead to changes in the protein it codes for.
How much affect do mutations have?
Little or no effect on protein. Some will change it to such a small extent that its function/appearance is unnafected.
What affects can some mutations have?
Seriously affect a protein.
Mutation will code for an altered protein with a change in its shape.
This could affect its ability to perform function.
Example of how the mutation can affect a protein?
If shape of an enzyme active site is changed its substrate may not bind to it.
Structural proteins like collagen could lose their strength if their shape is changed making them useless to provide structure and support.
What happens if there is a mutation in non-coding DNA?
Alters how the gene is expressed.
Give the three different types of mutations
Insertions
Deletions
Substitutions
Describe insertions.
New base is inserted into DNA base sequence where it shouldn’t be.
An insertion changes the ways the groups of three bases are read which can change the amino acids they code for.
Insertions can change more than one amino acid as they have a knock on effect on bases further in the sequence.
Describe Substitutions.
when a ransom base in the DNA base sequence is changed to a different base.
Describe Deletions.
When a random base sequence is deleted from the DNA base sequence.
Like insertions they can change the way that the base sequence is read and have knock on effects further down the sequence.
Define sexual reproduction.
genetic information from two organisms a father and mother is combined to produce offspring which are genetically different to either parent. Involves fusion of male and female gametes, as there are two parents te offspring contain a mixture of their parents genes.
In sexual production what do the mother and father produce?
Gametes, by meiosis eg: egg and sperm cells in animals.
In humans how many chromosomes does each gamete contain?
23 chromosomes half the number of chromosomes in a normal cell. Instead of having having two of each chromosome a gamete has just one each)
How do the gametes then create a cell with the full number of chromosomes?
The egg the mother and the sperm the father, then fuse together (fertilisation) to form a cell with the full number of chromosomes half from the father and half from the mother.
Why the offspring inherits features from both parents.
its recieved a mixture of chromosomes from its mum and its dad and its the chromosomes that decide how you turn out.
What produces a variation in offspring?
Mixture of genetic information produces variation in offspring.
How do flowering plants reproduce?
They have egg cells, but the sperm is known as pollen.
quick asexual reproduction
Theres only one parent so the offspring are geneticaly identical to their parent.
It happens by mitosis, an ordinary cell makes a new cell by diving in two.
In asexual reproduction what does the new cell contain?
Exactly the same genetic information as the parent cells its called a clone.
Definition of asexual reproduction.
there is only one parent.
no fusion of gametes
no mixing of chromosomes and no genetic variation between parent and offspring.
the offspring are genetically identical to their parent so they are clones.
What reproduces asexually?
Bacteria,some plants,some animals.
To make gametes with only half of the original number chromosomes what occurs?
Cells will divide by meiosis. It involves two cell divisions.
In humans where does meiosis occur.
Reproductive organs (the ovaries in the femals and the testes in the males)
Describe the process of meiosis.
-before cell starts to divide it duplicates its genetic information forming two armed chromosomes.
-one arm of each chromsomeis an exact copy of the other arm.
-after replication the chromosomes arrange themeselves into pairs.
-in the first division in meiosis the chromosome pairs line up in the centre of the cell.
-the pairs are then pulled apart so each new cell only has one copy of each chromosome.
some of the fathers chromosomes and some of the mothers chromosome go into each new cell.
-in the second division the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.
-you get 4 gametes each with only a single set of chromosomes in it.
-Each of the gamete is genetically different from the others as chromosomes get shuffled up in meiosis and each gamete only get half of them.
After two gametes have fused during fertilisation what happens to the new cell?
new cell divides by mitosis to make a copy of itself.
mitosis repeats many times to make lots of cells in an embryo
as the embryo develops the cells differentate into the different types of specialised cell that makes a whole organism
Give four advantages of sexual reproduction
-offspring have a mixure of two sets of chromosomes.
the organism inherits genes and features from both parents which produces variation in offspring.
-Variation increases the chance of species surviving a change in enevironment. While a change in environment may kill some, it’s likely variation will lead to some offspring being able to survive in new environment so they have a survival advantage.
-individuals have characteristics which make them better adapted to environment they have beter chance of surviving. So are more likely to breed succesfully and pass genes and characteristics. Thus known as antural selection.
-Use selective breeding to speed up natural selection. This allows us to produce animals with desirable characteristics. Selective breeding when inidviduals with desirable charachteristics are bred to produce offspring with desirable charachterisitics So we can increase food production eg:breeding animals which produce lots of meat.
Asexual reproduction advantages.
Only needs one parent
Uses less energy than sexual reproduction, as orgainisms don’t have to find a mate.
faster than sexual reproduction
Many identical offspring can be produced in favourable conditions
Does the parasite which causes malaria reproduce asexually or sexually?
Malaria is caused by a parasite thats spread by mosquitos.
- When a mosquito carrying the parasite bites a human the parasite is transferred to a human.
- The parasite reproduces sexually wen in the mosquito and asexually when in the human host.
Does fungus produce asexually or sexually?
both.
These species release spores which can become new fungiwhen they land in a specific place.
Spores can be produced sexually and asexually.
Asexually produced spores form fungi that are genetically identical to the parent fungus.
Sexually produced spores introduce variation and are produced in response to unfavourable change in environment increasing the chance the population will survive the change.
Give an example of a plant reproducing asexually.
-strawberry
Strawberry plants produce runners.
They are stems that grow horizontally on the surface of the soil away from the plant.
At various points along the runner a new strawberry plant forms that is identical to original.
Give an example of a plant reproducing asexually.
-bulbs
plants that grow from bulbs eg daffodils,
New bulbs can form from main bulb and divide off
each new bulb can grown into a new identical plant.
What is the role of all 22 chromosomes and the 23rd?
22 are matched pairs of chromosomes that controll charachteristics
23 pair are labelled XY or XX they are the two chromosmes that decide your sex
What is the male chromosome?
XY
Y chromosomes cause male characteristics
What is the female chromosome?
XX
combination of two X allows female charateristics to develop.
When making sperm what happens?
X and Y chromosomes are drawn apart om the fist divsion of meiosis
50% chance each sperm gets an x chromosome and 50% chance it gets a y chromosome.
When making eggs what happens?
Original cell has 2 x chromosomes.
So all the eggs have one x chromosome
What do genetic diagrams show?
Models sued to show all the possible genetic outcomes when you cross together different genes or chromosomes.
What genes you inherit control what?
What characteristics you develop.
What do different genes control?
Different characteristics some characteristcs are controlled by a single gene eg:mouse fur colour and red green colour blindess in humans.
What are some characteristics controlled by?
A single gene, eg:mouse fur colour, red green colour blindless in humans
What are most characteristics controlled by?
Several genes interacting,
What is an allele?
Different versions of a gene. There are 2 alleles for every gene in your body (one on each chromosome in a pair.)
