Topic 6- Inheritance, Variation and Evolution Flashcards
What does DNA stand for?
Deoxyribonucleic acid.
What is DNA?
It’s the chemical that all of the genetic material in a cell is made up from.
What does DNA contain?
Coded information- basically all the instruction to put an organism together and make it work.
What does your DNA determine?
The inherited characteristics you have.
Where is DNA found in?
The nucleus of animal and plant cells, in really long structures called chromosomes.
What do chromosomes normally come in?
Pairs
Describe DNA.
It is a polymer. It’s made up of 2 strands coiled together in the shape of a double helix.
What is a gene?
A 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?
Only 20 amino acids are used, but they make up thousands of different proteins.
What do genes tell cells to do?
Genes tell cells in what order to put the amino acids together.
Give another thing DNA determines.
What proteins the cells produce, e.g. haemoglobin, keratin. This in turn determines what type of cell it is, e.g. red blood cell, skin cell.
What is genome?
It is the entire set of genetic material in an organism.
What is understanding the human genome important for?
Science and medicine.
Why is understanding the human genome important? (1)
Genes linked to diseases can be identified. This helps us better understand inherited diseases, so we can develop effective treatments.
Why is understanding the human genome important? (2)
Tiny differences in people’s genomes can be studied. This helps us trace the migration patterns of past human populations
What are DNA strands?
They are polymers made up of lots of repeating units called nucleotides.
What are nucleotides?
Repeating units
What does each nucleotide consist of?
A sugar, a phosphate group and one ‘base’.
What forms a ‘backbone’ to the DNA strands?
The sugar and phosphate groups in the nucleotides.
Which 4 different bases joins to each sugar?
A, T, C, G
What does each base link to?
Each base links to a base on the opposite strand in the helix.
Give 2 examples of complementary base pairing.
- A always pairs up with T
2. C always pairs up with G
What decides the order of amino acids in a protein?
It’s the order of bases in a gene that decides the order of amino acids in a protein.
What does each amino acid code for?
Each amino acid is coded for by a sequence of 3 bases in the gene.
What do amino acids joined together make?
Various proteins, depending on the order of the gene’s bases.
What do non-coding parts of DNA do?
Switch genes on and off, so they can control whether or not a gene is expressed.
Where are proteins made?
In the cell cytoplasm on tiny structures called ribosomes.
What do ribosomes use to make proteins?
The code in the DNA.
Why can’t DNA move out of the nucleus?
Because it’s really big.
How do the ribosomes make proteins? (1)
The cells need to get the code from the DNA to the ribosome.
How do the ribosomes make proteins? (2)
This is done by using a molecule called mRNA- which is made by copying the code from DNA.
How do the ribosomes make proteins? (3)
The mRNA acts as a messenger between the DNA and the ribosomes- it carries the code between the two.
How do the ribosomes make proteins? (4)
The correct amino acids are brought to the ribosomes in the correct order by carrier molecules.
How can a protein perform the task it’s meant to do?
When a chain of amino acids has been assembled, it folds into a unique shape which allows the protein to perform the task it’s meant to do.
Give 3 examples of types of proteins.
- Enzymes
- Hormones
- Structural proteins
When does a gene mutate?
Occasionally
What is a mutation?
It is a random change in an organism’s DNA. They can sometimes be inherited.
How does a mutation occur?
Continuously, they can occur spontaneously.
What increases the chances of mutation?
By exposure to certain substances or some types of radiation.
What can mutations do?
Change the sequence of the DNA bases in a gene, which produces a genetic variant.
What is a genetic variant?
A different form of the gene.
What can mutations to a gene sometimes lead to?
Changes in the protein that it codes for.
What effects do most mutations have?
Very little or no effect on the protein.
What effect do some mutations have?
Some will change it to such a small extent that its function or appearance is unaffected.
What affect do some mutations have? (2)
It can seriously affect a protein. Sometimes, the mutation will code for an altered protein with a change in its shape. This could affect its ability to perform its function.
What happens if there is a mutation in the non-coding DNA?
It can alter how genes are expressed.
Give 3 types of mutations.
- Insertions
- Deletions
- Substitutions
What are insertions?
They are where a new base is inserted into the DNA base sequence where it shouldn’t be.
What can an insertion change?
It changes the way the groups of three bases are ‘read’, which can change the amino acids that they code for.
How can an insertion change more than 1 amino acid?
The have a knock- on effect on the bases further on in the sequence.
What are deletions?
They are where a random base is deleted from the DNA base sequence.
What do deletions do?
They change the way that the base sequence is ‘read’ and have knock- on effects further down the sequence.
What are substitutions?
They are when a random base in the DNA base sequence is changed to a different base.
What is sexual reproduction?
It is where genetic material from 2 organisms is combined to produce offspring which are genetically different to either parent.
What does a mother and a father produce in sexual reproduction?
They produce gametes by meiosis- e.g. egg and sperm cells in animals.
How many chromosomes are there in gamete?
23 chromosomes
What is fertilisation?
When the egg and the sperm cell fuse together to form a cell with the full number of chromosomes.
What does the mixture of genetic information produce?
Variation
Describe asexual reproduction.
There’s only one parent. There’s no fusion of gametes no mixing of chromosomes and no genetic variation between parent and offspring.
Describe the offspring in asexual reproduction.
The offspring are genetically identical to the parent- they’re clones.
Give an example of a living thing which reproduces asexually/.
Bacteria
What is cystic fibrosis?
It is a genetic disorder of the cell membranes.
What is the result of cystic fibrosis?
It results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas.
What allele causes cystic fibrosis?
A recessive allele, ‘f’, carried by about 1 person in 25.
What is polydactyly?
It is a genetic disorder where a baby’s born with extra finders or toes.
What allele causes polydactyly?
Dominate allele
What does IVF stand for?
In vitro fertilisation
What happens during IVF?
Embryos are fertilised in a laboratory, and then implanted into the mother’s womb.
What can you do with an embryo before implanting it during IVF?
It’s possible to remove a cell from each embryo and analyse its genes. Many genetic disorders can be detected this way.
Give another way of testing for disorders.
It’s also possible to get DNA from an embryo in the womb and test that for disorders.
Give an argument for embryonic screening (1).
It will help to stop people suffering.
Give an argument for embryonic screening (2)
Treating disorders costs the Government (and the taxpayers) a lot of money.
Give an argument for embryonic screening (3)
There are laws to stop it going too far. At the moment parents cannot even select the sex of their baby.
Give an argument against embryonic screening (1).
It implies that people with genetic problems are ‘undesirable’- this could increase prejudice.
Give an argument against embryonic screening (2).
Screening is expensive.
Give an argument against embryonic screening (3)
There may come a point where everyone wants to screen their embryos so they can pick the most ‘desirable’ one.
How did Carl Linnaeus group living things in the 1700’s?
According to their characteristics and the structures that make them up.
Describe the Linnaean system.
Living things are first divided into kingdoms. The kingdoms are then subdivided into smaller and smaller groups.
Give 6 subdivisions of kingdoms (in order).
- Phylum
- Class
- Order
- Family
- Genus
- Species
How were scientists able to put forward new models of classification?
- Knowledge of the biochemical processes taking place inside organisms developed.
- Microscopes improved.
What did Carl Woese propose in 1990?
Three-domain system
How did Carl Woese know that some species are not closely related?
Using evidence gathered from new chemical analysis techniques such as RNA sequence analysis.
Give examples of the 3 domains in the three- domain system.
- Archaea
- Bacteria
- Eukaryota
What does the Eukaryota domain include?
It includes a broad range of organisms including fungi, plants, animals and protists.
What does the Bacteria domain contain?
True bacteria like E. coil. There are biochemical differences between the Bacteria domain and the Eukaryota domain.
What did the organisms in the Archaea domain were once thought to be?
Primitive bacteria
What are the organisms in Archaea?
They’re different type of prokaryotic cell.
Where were Archaea organisms once found in?
Extreme places such as hot springs and salt lakes.
Describe the binomial system.
The first part refers to the genus that the organism belongs to. The second part refers to the species.
What information does the first part of the binomial system give?
It gives you information on the organism’s ancestry.
How is the binomial system able to avoid potential confusion?
The scientists in different countries or who speak different languages all refer to a particular species by the same name.
What does an evolutionary tree show? (1)
It shows how scientists think different species are related to each other.
What does an evolutionary tree show? (2)
They show common ancestors and relationships between species.
