Biology 1: You and Your Genes Flashcards
DNA
Large (polymer) molecule found in the nucleus of all body cells – it’s sequence determines genetic characteristics, such as eyecolour, and gives each one of us are unique genetic code
Chromosomes
Threadlike structures in the cell nucleus that carry genetic information – each chromosome consists of DNA wound around a core of protein
What are DNA strands made of
Bases as well as phosphate groups and sugar molecules
Where are chromosomes found
In the nucleus
How many genes do we have in our chromosomes
Between 20,000 and 25,000 genes in our chromosomes
Why does the order of the bases in DNA strand matter
It determines the order of amino acid’s in a protein
Which Groups do proteins falling into
- functional proteins
* structural proteins
Structural protein
A protein, such as collagen, whose function is to build tissues
Functional protein
A protein such as an enzyme that speeds up a chemical reaction
What does the human Genome project do
Has identified the location of all the jeans on human chromosomes. We call the complete gene set of an organism it’s genome
What does the Human Genome project help us to understand
How do you control or characteristics and development, and can lead to certain diseases
What is the Human Genome project ethical implications
some drug companies want to patent or own jeans. They could then charge of a scientist money to this get the genes, which would restrict research
What factors are controlled by our genes
- Characteristics, for example dimples
- environment for example the presence of scars and dyes hair
- or a combination of these are bodyweight
Where do our genes come from
We inherit dreams from my parents, so we’re similar but not identical to each parent
Variation
Differences between individuals belonging to the same species
What does differences in genes produce
Variation in offspring
Continuous variation
Variation in organisms of features that take any value, for example height
Characteristics controlled by several genes working together
These characteristics will show continuous variation across the population sample the continuous range of colours and different heights
What are the names of a particular characteristic
Genotype
Phenotype
Genotype
And individuals genetic make up, such as whether they are homozygous or heterozygous for a particular gene
Phenotype
The physical expression of the gene; different genotypes can give the same phenotype
What colour genotype refer to
The whole of an individual’s jeans or (more often) the jeans for a particular characteristic,such as if they have dimples the genotype is usually written two letters for example DD
What does the phenotype depend on
The persons genes, but may also be affected by how these interact with the environment
What about identical twins genotypes
Identical twins have identical Genotypes because they develop after fertilised egg splits into two
How do studies of identical twins help us
To understand the effect of the environment on a persons genotype
How are chromosomes arranged
In pairs
Many chromosomes do humans cells have
23 pairs. A total of 46 chromosomes
Where did these 23 chromosomes come from
Excels are eggs (over) and sperm. These have 23 chromosomes, one from each pair
Human baby
The human baby that develops as a combination of genes from its mother and father
Fertilisation
The moment when the nucleus of a sperm fuses with nucleus of an egg
Describe the gene position for chromosomes
Pairs of chromosomes have jeans for the same characteristic at identical positions of each chromosome of the pair
How does mutation occur
Changes to our DNA sometimes occur, causing a mutation. This can take place when sex cells are being made, or after fertilisation
Chromosome mutation
One type of mutation is called chromosome mutation. This results in an individual having extra chromosomes for example a person with an extra chromosome 21 will have Down’s syndrome
How does the combination of chromosomes vary
- The combination of chromosomes in an egg or sperm will always be different for example in an egg crime is own one could have been inherited from the mother, while crime is own two and three could have been inherited from the father etc. So, the combination of chromosomes (and therefore jeans) will be unique to that person – unless he or she has an identical twin
- environmental effects will also add to the variation
Alleles
Different versions of the gene on a pair of chromosomes
Homozygous
An individual who has identical alleles for an inherited characteristic
Heterozygous
And individual who has two different alleles for an inherited characteristic
The order of size from largest to smallest
Cell Nucleus Chromosomes DNA Gene Base
Dominant (allele)
There allele that is always express, irrespective of the other allele in the pair
Recessive (allele)
An allele that is only expressed if the other allele in the pair is also a recessive; it is hidden if the other allele in the pair of them is dominant
Genes
A section of DNA that codes for a particular characteristic by controlling the production of a particular protein or part of protein by cells
What are dominant alleles written in
Uppercase letters in genetic diagram for example
H for hairy toes
What are recessive traits written in
Lowercase letters in genetic diagrams
Punnet square
A diagram that can be used to work out the probability of outcomes resulting from a genetic cross
Family tree diagram
Chart showing relationships between family members of different generations of the family, which can be used to show inheritance of genetic characteristics
What is a family tree diagram useful for
When tracing agent at it this order, such as Huntington disease over generations
Pair of chromosomes determine our sex
The 23rd pair
Female chromosome
A female has two X chromosomes,written XX
Male chromosome
Are mail has an X and Y chromosome, written XY
Punnet square chromosome outcomes
- each egg cell produced by female will have an X chromosome
- Half of the sperm cells produced by a male will happen X Half of the sperm cells produced by a Male will have an X chromosome and half all have a Y chromosome
So in theory 50% of babies will be female and 50% will be male
What determines whether an embryo is male or not
Presence of a Y gene on the Y chromosome– The sex determining gene – That determines whether the embryo is male or not (it triggers the development of testes in the embryo). In the absence of the Y chromosome, ovaries develop
What causes sex linked disorders
Because of the shape of the sex chromosomes, there are parts of the X-chromosome that have no Y chromosome. If a defective gene it’s found on this part of the excrement time, this can result in a sex linked disorder
Examples of sex linked diseases
Haemophilia (a blood clotting disorder) and red green colour blindness, are far more likely to be present in males
How are other disorders caused
Disorders are caused by defective or faulty alleles
What is Huntington’s disease caused by
Huntington’s disease is a dominant disorder, I.E.the presence of a single dominant allele will cause of the disease. It occurs in to age. Symptoms include tremors (uncontrollable shaking), memory loss, inability to concentrate and mood changes
Recessive disorders
Both alleles on the chromosome pair must be recessive for a person to get a recessive disorder, such as cystic fibrosis. Symptoms include the production of thick gluey mucus that affects the lungs and makes digestant food difficult, breathing problems and chest infection.
Carrier
Someone who carries a gene but does not themselves have the characteristic
A recessive single gene disorders
Recessive single gene disorders, a person with a normal and defective allele will be normal (because the normal gene is dominant), but they will be a carrier
Genetic screening
Testing large numbers of individuals for Jean, such as the gene for a genetic disorder
Zygote
The cell phone by the fusion of a male and female gamete at fertilisation
What’s is genetic screening used for
Is used for a particular disorder even when there is no history of it in the family. It is hoped this will minimise the damage shut such disorders can cause. For example, the heel prick’ blood spot test’ is used on most newborn babies to diagnose rare genetic disorders
Genetic Testing
Testing an individual for the gene for a genetic disorder
When is genetic testing used
Genetic testing of individuals is carried out when a genetic disease such as cystic fibrosis runs in the family. This may allow people to get treatment for the disease or plan for the future
What does genetic testing raise
Ethical questions for example if a person has Huntington’s disease should they tell their employer, insurance company of family?
Cell sampling
Removal of a small number of fetal cells, for example from the placenta all the amniotic fluid, for testing
When may genetic testing during pregnancy involve cell sampling
• amniocentesis (collecting cells from the developing fetus which are present in amniotic fluid)
• chorionic villa sampling (testing a sample of cells taken from the presenter)
Both tests carry risk – around 1% of babies are miscarried as a result of genetic testing
Embryos
And organism in the early stages of development which began as a zygote and will become a foetus
Fetus
Later stage embryo of an animal; the body parts are recognisable
In vitro fertilisation (IVF)
Production of embryos in vitro fertilisation allows doctors to check the genetic make up of the embryos prior to implementation this is known as embryo screening
Pre-implantation genetic diagnosis (PGD)
Genetic testing of embryos created by in vitro fertilisation for a genetic disorder, so that healthy embryos can be transferred into the mothers uterus
How is procedure is like PGD done
Procedures like PGD an embryo research carefully monitored in the UK. Guidelines for clinics and research centres over ethical and moral consideration of embryo use
When parents likely to pass on a genetic abnormality they …
- May not decide to have a family
* May need to decide on whether to continue with the pregnancy or terminate it
What is wrong with the genetic tests
Types of genetic tests may give false negative results and may sometimes give false positive results (where the tests is positive but the person does not have the disorder)
Clones
Organism genetically identical to another
ASexual reproduction
Reproduction involving only one parent; offspring are genetically identical to the parent
Bacteria
Single celled microorganisms, some of which may invade the body and cause disease
How come plants reproduce asexually
- using runners, (for example strawberries) – shoots sent out that grow into identical plants
- producing bulbs (for example daffodils)
Identical twins
Identical twins are human clones produced when a fertilised egg splits, resulting in to genetically identical individuals
Differences between clones
As clones have identical DNA, any differences between individuals in a clone and their parent must be a result of the environment and not genes
The advantages of producing clones/asexual reproduction are that:
- successful characteristics are seen in offspring
- Asexual reproduction is used for where plants and animals live in isolation
Disadvantage of producing clones/asexually
Is that there is no genetic variation. This means that if conditions change or there is the disease, the population would be wiped out
Example of artificial animal cloning
Dolly the sheep and snuppy the dog
How did artificial animal cloning happen
- The nucleus from a body cell is extracted and inserted into an egg cell that has had its nucleus removed. This gives the eggs out a full set of dreams about having been fertilised
- The embryo is implanted into a suitable surrogate mother
The law
It is illegal to create close of humans in many countries, including the UK
Differentiation
The change of unspecialised body cell into a particular type of cell
What does the human embryo develop from
A human embryo develops from the single self. This cell divides over and over again as the baby develops. Most of the cells become specialised to do different jobs a process called differentiation
Stem cells
Unspecialised body cells that can develop into other, specialised cells
Adult stem cells
Unspecialised body cells that can develop into other, specialised cells that the body needs
What can adults stem cells do
- Can repair or replace certain cell types for example bone marrow cells are able to develop into different types of blood cells
- are used to treat various diseases, but have limited uses
Embryonic stem cells
Souls in all from an embryo with the potential to become any other type of cell in the body
Controversy about embryonic stem cells
- they are usually taken from a news embryos following fertility treatment
- their use involves the destruction of the embryo
Recent research on don’t body cells
Recent research is focusing on reprogramming adult body cells into stem cells, I’m collecting cells from the umbilical cord blood when a baby is born
What could stem cells be used in
- The testing of new drugs
- understanding how cells become specialised in the early stages of human development by switching on and off of particular genes
- renewing damaged or destroying cells in spinal injuries, parties, Alzheimers disease and Parkinson’s disease
