You and your genes Flashcards
What carries the instructions for the proteins that are needed to make your cells to work?
Genes
What chemical makes up a gene?
DNA (DeoxyriboNucleic Acid)
What are the coils of DNA called?
Chromosones
What is the shape of a chromosome?
Double helix
How do you tell the sex of a chromosome?
Take off its genes. In mammals, the y chromosome makes male, XX is female.
Where would you find the chromosomes?
In the cell nucleus
How are genes coded?
The order of the bases determines the order of the amino acids in the protein
What two groups of proteins are coded on genes?
Functional proteins and structural proteins.
What is a functional protein?
A protein needed to make the body function, eg enzymes, hormones, antibodies
What is a structural protein?
A protein that is part of the structure of the body, eg skin (keratin) or collagen (found in skin, ligaments)
What was the project to map the human genes called?
The human genome project
What is the complete set of genes of an organism called?
The genome
What controls the characteristics of an organism?
Genes, environment, or a combination.
What are the ethical considerations of the human genome project?
Some companies want to patent genes. They would then “own” genes and could charge other scientists to investigate those genes. This would restrict research.
What is the consequences of differences in genes?
Variations within the species.
How many genes control each characteristic?
It can be one, or many.
If there are many genes controlling a characteristic how is the characteristic expressed within the population?
There will be continuous variation within the population, eg height.
What is the genotype?
The genes of an organism, usually expressed as two letters, eg Ee
What is the phenotype?
The observable physical characteristic of the organism
What is the phenotype affected by?
Genes and environment.
Why are studies on identical twins so valuable?
It enables research into the effects of the environment on an organism.
How many pairs of chromosomes does the human have?
23
How many chromosomes does the human have?
46
How many chromosomes in a human sex cell?
23
What do a sperm cell and an egg form when they combine?
A zygote
What is the process of the joining of egg and sperm?
fertilisation
How many chromosomes in the human zygote?
46
What are changes to DNA called?
Mutation
Why do brothers and sisters vary when they have the same parents?
It is random which chromosome they inherit from each parent, so the chance of getting the same mixture is 1 in 2 to the power of 46
What is an allele?
The different forms in which a gene controlling a characteristic can occur,
If an organism has the same allele on each chromosome for a particular characteristic this is called …..
Homozygous
If an organism has different alleles on each chromosome for a particular characteristic this is called ….
Heterozygous
If an allele is expressed when there are two different alleles present this is called…
Dominant
Dominant alleles are written as ….. in genetic diagrams
A single capital letter
Recessive alleles are written as … in genetic diagrams
A single lower case letter
For the recessive trait to show there must be at least …. recessive alleles present
Two
For the dominant trait to show there must be at least …. dominant allele present
One
What does a Punnett square enable you to show?
The probability of two parents producing different types of offspring
How is human sex (normally) determined?
By chromosome 23
What is the female chromosome shown as in genetic diagrams?
XX
What is the male chromosome shown as in genetic diagrams?
XY
What causes a sex-linked disorder?
The y chromosome is shorter. If a defective gene is found on the part of the X chromosome that has no matching allele on the Y chromosome then that gene must be expressed in boys, even if it is recessive.
What determines the sex of a baby?
The presence of the Y chromosome, without it the baby will be female.
Name a genetic disorder that is dominant
Huntington’s
Name a genetic disorder that is recessive
cystic fibrosis
What is a carrier of a genetic disorder?
A person that has one copy of the defective gene that can be passed to offspring but they do not show the disorder.
What is screening for genetic disorders?
It is when the whole population is tested even if there is no history in the family, eg the heel prick test on babies.
What is genetic testing?
The testing of an individual for a genetic gene, usually done when there are reasons to believe there is a problem, eg family history, or abnormal development in a baby.
What ethical questions are raised by genetic testing?
One big one is the question whether the person has to disclose he information to, for instance, an employer, or an insurance company, and whether the information can be used to make decisions about whether to employ/insure.
How is genetic testing in pregnancy done?
Amniocentesis or chorionic villus sampling
What is amniocentesis?
Collecting fetal cells from the amniotic fluid by using a needle through the mum’s abdomen
What is chorionic villus sampling
Testing a sample of fetal cells from the placenta (usually via the vagina).
What is the risk of miscarriage due to genetic testing?
About 1%
What is embryo screening?
Checking embryos produced by IVF prior to implantation
What is the process of screening embryos for genetic defects called?
Pre-implantation genetic diagnosis (PGD)
Is there any control over the production of human embryos?
In the UK there are strict guidelines.
What choices to parents with a genetic abnormality face?
They may decide not to have children, or they may face the choice of terminating a pregnancy
Are genetic tests 100% reliable?
No, both false positives and false negatives occur
What are clones?
Genetically identically individuals
If an organism clones itself, what is this called?
Asexual reproduction
Can human beings have clones?
Yes, identical twins are clones
What are the advantages of asexual reproduction?
All the offspring have the successful genes; a single animal can colonise a new area
What are the disadvantages of asexual reproduction?
Lack of variation means that any challenge to the species could wipe it out - eg climate change/disease.
Can mammals be cloned?
Yes
Is is legal to clone human beings?
Not in the UK
How was Dolly cloned?
A nucleus from one of her body cells was extracted and injected into an egg cell that had already had its nucleus removed. This zygote is stimulated to start dividing and the resultant embryo is implanted into a surrogate mother.
What is the process of a cell becoming specialised called?
Differentiation
What are the unspecialised cells in the embryo called?
Embryonic stem cells
What are adult stem cells?
Cells that can develop into a limited range of different cell types, eg bone marrow stem cells to blood cells
Why is the use of embryonic stem cells controversial?
They come from unused embryos from fertility treatments,, and the embryo is destroyed.
What are the uses of stem cells?
Testing new drugs; understanding the specialising of cells by the switching on/off genes; renewing damaged cells in the spine/heart
