B6 - DNA and inheritance Flashcards
what type of molecule is dna *
a polymer
what do genes do
code for a particular sequence of amino acids in order to make a specific protein
genome
the complete set of dna for an organism
3 reasons we study the human genome
- to search for genes linked with different types of diseases
- to understand inherited disorders and their treatment
- to trace human migration patterns from the past
mutation
a change in the dna sequence which can often result in changes to amino acids
what is dna profiling
the process through which a specific dna pattern is obtained from aw person or sample of bodily tissue
uses for dna profiling
- identifying disaster victims
- identifying the probable origins of bodily fluid samples associated with a crime scene
what are nucleitides
repeating monomers that make up dna
4 bases in dna
- adenine A
- thymine T
- cytosine C
- guanine G
3 parts of a nucleotide
- phosphate
- pentose sugar
- nitrogenous base
draw a nucleotide
see draw*
what is a triple codon
a sequence of 3 bases - these code for a particular amino acid
what shape is dna
double helix
why can dna be described as a double helix shape
made from two strands which twist around each
other
what is a polymer
A polymer is a large molecule made from many smaller molecules called monomers.
what is a gene
A gene is a small section on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
how are chromosomes usually found and how many are there
In human body cells the chromosomes are normally found in
pairs. Each cell has 23 pairs of chromosomes.
human genome project
The Human Genome Project (HGP) was an international scientific research project set up to map all the genetic information in a human being. was completed in 2003
what does adenine always pair with
thymine
what does thymine always pair with
adenine
what does cytosine always pair with
guanine
what does guanine always pair with
cytosine
what is it called each base only pairs with one other
complimentary pairing
4 examples of uses for proteins in the body
- hormones
- enzymes
- antibodies
- structural components i.e collagen
how many different amino acids are in the body
20
what does the sequence of a triple codon determine
A sequence of three bases is the code for a particular amino acid.
The order of the bases controls the order in which amino acids are
assembled to produce an individual protein.
draw a diagram of a dna strand
see draw*
7 steps of how dna becomes protein
- Part of the DNA unravels.
- Enzymes make a copy of the DNA strand. This is
called mRNA. - mRNA moves out of the nucleus into the cytoplasm.
- The mRNA travels to the ribosome in the cytoplasm.
- Ribosomes translate each set of 3 bases into amino acids according to the
mRNA template. - Amino acids are found in the cytoplasm. The correct amino acid for each set of
3 bases is brought to the ribosome by a carrier molecule. - A long chain of amino acids form. Their specific order forms a specific protein
3 steps for how gene code gets to the ribosome
- Part of the DNA unravels.
- Enzymes make a copy of the DNA strand. This is
called mRNA. - mRNA moves out of the nucleus into the cytoplasm.
4 steps for protein synthesis
1/. The mRNA travels to the ribosome in the cytoplasm.
2/ Ribosomes translate each set of 3 bases into amino acids according to the mRNA template.
3/ Amino acids are found in the cytoplasm. The correct amino acid for each set of 3 bases is brought to the ribosome by a carrier molecule.
4/ A long chain of amino acids form. Their specific order forms a specific protein
what happens once a protein chain is complete that allows it to carry out its function
When the protein chain is complete, it folds up to form a unique
shape. This unique shape allows the protein to carry out its role effectively
how frequently to mutations occur
Mutations occur continuously during cell division
why are most dna mutations harmless
Most of the time when a mutation occurs, the change to the coding of DNA is so slight it does not affect the protein being made. The proteins appearance and function are unchanged.
what could happen if a mutation altered the protein of an enzyme
The active site of an enzyme may have a changed shape and then
the enzyme will not be able to bind to the substrate. The enzyme will no longer function
what could happen if a mutation altered the protein of a structural protein
Structural proteins such as keratin or collagen may also lose their
strength if their shape was altered.
padlet bio slide 18/69
What does Meiosis lead to?
Meiosis leads to non-identical cells being formed.
What does Mitosis lead to?
Mitosis leads to identical cells being formed.
State the process involved when male and female gametes fuse together
Sexual Reproduction
sexual reproduction
when male and female gametes fuse together
Recall the male and female gametes found in animals.
Sperm and Egg Cells
Recall the male and female gametes found in plants.
Pollen and Egg Cells
What does mixing of genetic information lead to?
Variation of offspring
Which process are gametes formed?
Meiosis
Name the type of reproduction involves only one parent and no fusion of gametes.
Asexual Reproduction
State the term used to describe genetically identical offspring.
Clones
Which process are clones formed?
Mitosis
What happens to the number of chromosomes during meiosis?
They halve in number (23 Chromosomes)
What happens to the number of chromosomes during fertilisation?
They are restores to the full number (46 Chromosomes)
What is formed after cells in reproductive organs divide by meiosis?
Gametes
What happens to genetic information when gametes are formed?
Copies of the genetic information are made.
How many times does the cell divide to form 4 gametes?
The cell divides twice to form four gametes.
After meiosis are genetic information the same or different?
All gametes are genetically different from each other.
How do all cells except gametes divide?
Mitosis
What happens to cells as the embryo develops?
The cells differentiate
What type of reproduction leads to increased variation in offspring.
Sexual Reproduction.
What needs to happen for variation to give a survival advantage by natural selection.
Environment Changes.
State way humans can increase food production by natural selection.
Use Selective Breeding.
How many parents are needed in asexual reproduction?
Only one parent needed.
Why is asexual reproduction classes as time and energy efficient?
You do not need to find a mate.
sexual or asexual
Which type of reproduction is faster?
Asexual Reproduction.
Recall the type of offspring produced after asexual reproduction.
Identical Offspring.
How do malarial parasites reproduce in humans?
In humans = Asexually
How do malarial parasites reproduce in mosquitos?
In mosquitos = Sexually
How do fungi reproduce asexually?
By Spores.
How to fungi reproduce to give variation?
Sexual Reproduction = Variation
Name the plant which reproduces asexually.
Strawberry
Name the plant which reproduces by bulb division.
Daffodils.
bulb division
Some plants (eg. daffodils) reproduce via bulb division (new bulbs form from the main bulb underground and then grow into new identical offspring plants)
State the structure of DNA
Double Helix
What is the genome of an organism?
The entire genetic material (DNA) of that organism.
Recall the material found in the nucleus of a cell.
Genetic materlal (DNA)
Why is DNA classed as a polymer?
DNA is made up of two strands of nucleotides in a double helix
State which structure DNA is contained in.
Chromosomes
What is a Gene?
A gene is a small section of DNA on a Chromosome.
What do Genes code for?
Genes code for a particular sequnce of Amino Acids, to make a specific protein.
What is the Genome?
The genome of an organism is the entire genetic material of that organism.
In DNA, what does each nucleotide contain?
Sugar and phosphate group with a base attached to the sugar.
Name the bases found in DNA.
Adenine, Cytosine, Guanine & Thymine.
How many bases in DNA are needed to code for an Amino Acid?
3 bases = an Amino Acid (also a Gene).
What happens when the order of bases are changed in DNA?
A different protein is made.
DNA is polymer, what is the monomer?
Nucleotides.
What happens to enzymes when the order of bases are changed in DNA?
Leads to change in shape of the enzyme and the active site.
How do genetic variants influence phenotype in non-coding DNA?
By altering how genes are expressed.
Recall the bases in DNA which form complementary pairs.
“C pairs with G.
A pairs with T.”
Which organelle in the cell synthesises proteins?
Ribosomes.
Which molecule adds specific amino acids to add to a growing protein chain?
Carrier Molecules.
Give 3 examples of proteins found in the body.
Enzymes, Hormones & Collagen.
How often do mutations occur?
continuosly and randomly
Do mutations always alter the proteins shape?why?
Most mutations do not lead to change in appearance or function.
What happens when a mutation leads to a change in the shape of an enzyme?
An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
What is a function of Non-Coding parts of DNA?
Can switch genes on and off.
What can variations in non-coding parts of DNA cause?
Affect how genes are expressed.
Define the term Allele.
Different forms of the same gene.
Define the term Dominant.
Will always produce the characteristic when present.
Define the term Recessive.
Requires two copies to be present to produce the characteristic
Define the term Homozygous.
When an organism has two alleles that are the same for an inherited characteristic
Define the term Heterozygous.
When an organism has two alleles that are different for an inherited characteristic.
Define the term Genotype.
The genetic makeup of an organism, controls the phenotype.
Define the term Phenotype.
Characteristics expressed by the organism.
Name the 2 characteristics controlled by a single gene.
Fur colour in mice and red-green colour blindness in humans.
When are dominant alleles expressed?
A dominant allele is always expressed, even if only one copy is present.
When are recessive alleles expressed?
A recessive allele is only expressed if two copies are present (therefore no dominant allele present).
not exact
How many genes are required in most characteristics?
Multiple Genes.
How do we predict the results of a single gene cross?
Using Probability.
In what form are the results of a genetic cross given?
Direct Proportion & Simple Ratios.
What do we use to extract and interpret information from a genetic cross or family tree?
Punnett Square Diagrams.
What are Punnett Square Diagrams used to make?
Predictions, using probability.
State the cause of inherited disorders.
Inheritance of certain alleles.
What is Polydactyly and what type of allele is it caused by?
Having extra fingers or toes and is caused by a dominant allele.
What is Cystic Fibrosis and what type of allele is it caused by?
A disorder of cell membranes and is caused by a recessive allele.
State an advantage of embryo screening & gene therapy.
Alleviate suffering.
Name a economic, social & ethical issues of embryo screening.
Expensive & implies people with disorders are undesirable.
What do the first 22 chromosomes control.
Characteristics.
State the pairs of chromosomes which determine a human’s sex.
“Females = XX
Males = XY”
What do we use to show sex inheritance?
Genetic Cross.
How could we influence the development of the phenotype?
Change in genotype or environment.
Define the term Variation.
Differences in the characteristics of individuals in a population.
What 3 reasons may there be a cause for variation in a population?
- The genes they have inherited (genetic causes)
- The conditions in which they have developed (environmental causes)
- A combination of genes and the environment.”
How much variation is found within a population?
Extensive variation can be found.
How to variants arise?
As a result of mutations.
How often to mutations occur?
Mutations occur continuously.
How often does a mutation lead to a new phenotype?
Very rarely.
What happens if a new phenotype is suited to an environmental change?
Can lead to a relatively rapid change in the species.
Define Evolution.
A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.
What term is used when all species of living things have evolved from simple life forms that first developed more than three billion years ago.
Theory of Evolution by Natural Selection.
What does natural selection of variants give rise to?
Phenotypes best suited to their environment.
What is the result when two populations of one species become very different in phenotype?
They can no longer interbreed to produce fertile offspring they have formed two new species.
Define Selective Breeding.
The process by which humans breed plants and animals for particular genetic characteristics.
What is the purpose of Selective Breeding?
To obtain offspring with desired characteristics from a mixed population.
Give an example of a useful characteristic in selective breeding.
- Disease resistance in food crops.
- Animals which produce more meat or milk.
- Domestic dogs with a gentle nature.
- Large or unusual flowers.”
What is the disadvantage of inbreeding?
Prone to disease or Inherited defects.
Define Genetic Engineering.
A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
Why are plant crops genetically engineered?
To be resistant to diseases or to produce bigger better fruits.
Why are Bacterial cells genetically engineered?
To produce useful substances such as human insulin to treat diabetes.
Name the process where genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
Genetic Engineering.
Recall the name of a crop which have had their genes modified.
GM Crops.
State the benefits of GM crops.
“Resistant to insect attack & herbicides.
GM crops have increased yield.”
State the disadavtages of GM crops.
“Negative effect on populations of wild flowers and insects.
Some people feel the effects of eating GM crops on human health have not been fully explored.”
State the steps of Genetic Engineering.
In Genetic Engineering:
* Enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus.
* The vector is used to insert the gene into the required cells.
* Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.
Recall the term used when small groups of cells from part of a plant to grow identical new plants.
Tissue Culture.
Recall the term used when an older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
Cuttings.
Recall the term used when splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
Embryo Transplants.
Name the scientist who proposed the theory of evolution by natural selection.
Charles Darwin
State the name of the journal in which Darwin published his ideas.
On the Origin of Species (1859).
Why was Darwin’s theory of evolution only gradually accepted?
”* The theory challenged the idea that God made all the animals and plants that live on Earth
* There was insufficient evidence at the time the theory was published to convince many scientists
* The mechanism of inheritance and variation was not known until 50 years after the theory was published.”
Name the scientist who proposed that changes that occur in an organism during its lifetime can be inherited.
Jean-Baptiste Lamarck.
Name the scientist who is best known for his work on warning colouration in animals and his theory of speciation.
Alfred Russell Wallace.
Name the scientist who is best known for his observation that inheritance of each cahracteristic is determined by “units”.
Gregor Mendel.
What is the modern day name given to mendel’s “units”.
Genes.
Why is Darwin’s theory now accepted?
It has been shown that characteristics are passed on to offspring in genes.
Define the term Fossils.
The ‘remains’ of organisms from millions of years ago, which are found in rocks.
How are Fossils formed?
”* From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
* When parts of the organism are replaced by minerals as they decay
* As preserved traces of organisms, such as footprints, burrows and rootlet traces.”
Why cannot scientists be certain about how life on Earth began.
Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.
What can we learn from Fossils?
How much or how little different organisms have changed as life developed on Earth.
How to we compare evolution between species.
Using evolutionary trees.
Define Extinction.
When there are no remaining individuals of a species still alive.
Why can bacteria evolve rapidly?
Bacteria reproduce at a fast rate.
How do bacterial pathogens produce new strains?
Through mutations.
What happens to bacterial strains which are resistant to antibiotics?
They are not killed.
What problems occur when bacterial pathogens produce new strains?
Bacteria strains might be resistant to antibiotics they then go onto survive and reproduce
Why can resistant bacterial strains spread?
People are not immune to it and there is no effective treatment.
Name a bacterial strain which is resistant to antibiotics.
MRSA.
How can we reduce the rate of development of antibiotics strains?
”* Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
* Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
* The agricultural use of antibiotics should be restricted.”
Why can we not keep up with the emergence of new resistant strains?
The development of new antibiotics is costly and slow.
Name the scientist who classified living things into groups based on structure and characteristics.
Carl Linnaeus.
Recall the catagories which Linnaeus classified living things.
Kingdom, phylum, class, order, family, genus and species.
Using the binomial system, how are organisms named?
Using their genus and species.
Why did new models of classification progress?
Evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed.
Name the scientist who developed the three domain system.
Carl Woese.
State the three domains found in Carl Woese system.
Archaea, Bacteria & Eukaryota.
Why do scientists use evolutionary trees?
To show how they believe organisms are related.
What type of data do scientists use for living organisms?
Current classification data.
What type of data do scientists use for extinct organisms?
Fossil Data.
