Biology - B1

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Order, from largest to smallest, starting with a cell.
Cell, Nucleus, Chromosome, Gene, Strand of DNA
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What is a gene?
A code for making certain a certain type of protein, different versions of proteins means different characteristics.
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Name the two types of proteins
Functional and Structual
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Give an example of each.
Functional = Enzymes, e.g. amylase, Structual = e.g. Collagen
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What is genotype and phenotype?
Genotype is all the genes an organism has and phenotype is all the characteristics that an organism displays.
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Name a characteristic only controlled by genes.
Eye colour or Dimples
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Name an environmental characteristic.
Scars, Piercings or Tattoos
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Name a characteristic controlled by both genes and the environment.
Weight
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How much DNA do a sperm or egg cell contain?
23 chromosomes
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What happens when the sperm fertilises the egg?
the 23 chromosmes from the egg combine with the 23 chromosomes from the sperm. This gives the fertilised egg 46 chromosomes like a body cell.
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What do the two chromosomes in a pair do?
They carry the smae genes and each gene is always found in the smae place on each chromosome. Because the two chromosomes in a pair came from different parents they might have different alleles which are different versions of the same gene.
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How much of a childs chromosomes come from each parent?
Half - they get some of their alleles from each parent.
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Do children look exactly like their parents?
No - they look a little bit like both parents but not exactly like either because they haven't got all the same alleles - some came from the other parent.
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Why don't two people look the same?
Everyone has a unique combination of alleles.
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What happens when people produce sperm or egg cells?
Their pairs of chromosomes seperate and go into different cells. Two chromosomes in a pair are never identical.
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How do each of the 23 chromosome pairs seperate?
Individually
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What does this mean for all sex cells produced by one individual?
They are probably all genetically different.
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What does this mean for brothers and sisters?
They look a bit alike but there are differences.
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Usually how many copies of a gene can be expressed in the phenotype / characteristics ?
Usually only one
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What are alleles?
Different versions of the same gene
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How many alleles do you have?
Two - one from each parent
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What does it mean if you are homozygous for a trait?
You have two of the same alleles for that particular gene
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What does it mean if you are heterozygous for a trait?
You have two different alleles for that particular gene.
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Explain about dominant and recessive alleles
Alleles can be dominant or recessive. Two dominant alleles for a gene or one dominant and one recessive would mean only the characteristic caused by the dominant allele would show. Both alleles have to be recesivve for that characteristic to show.
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How do genetic diagrams work?
Letters are used to reperesent alleles. Dominat alleles are represented through a capital letter and recessive alleles are show with a lower case letter.
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What chromosomes do men have?
XY - Y chromosme causes male characteristics
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What chromosmes do womem have?
** - Lack of Y chromosme causes female characteristics
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How many genes determine which sex organs you develop?
One
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What does the gene that makes an embryo into a male do?
It causes a specific protein to be produced
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What does the protein do?
It causes the development of testes instead of ovaries
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What do the testes do?
Prduce male sex hormones, which makes the rest of the male reproductive system to develop.
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What happens in females?
The protein is not produced so the embryo develops ovaries and the rest of the female reproductive system.
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What are genetic disorders caused by?
Faulty alleles - some are inherited faulty alleles passed by one or both parents.
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Give examples of genetic disorders caused by a faulty allele of a single gene?
Cystic Fibrosis and Huntington's Disease.
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What else can genetic disorders be caused by?
Recessive alleles. Most defective alleles responsible for genetic disorders are recessive. Cystic Fibrosis is a genetic disorder of all the cell membranes cause by a faulty recessive allele.
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What are the symptoms of Cystic Fibrosis?
Thick stick mucus in the gut, pancreas and air passages, breathing difficulty, chest infections, difficulty in digesting food.
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How many people carry the recessive allele for Cystic Fibrosis?
1 in 25 people.
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Because it is recessive, people who only have one copy of the allele won't show the symptoms - what are these people known as?
Carriers
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For a child to have a chance of inheriting the disease, what must they have?
Both parents must be carriers or sufferes.
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What is Huntington's Disease caused by?
A dominant allele
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What does the disorder cause?
Tremors, memory loss, mood changes, clumsiness, and poor concentration.
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Is there a cure?
No
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What is the chance of a child inheriting the disorder if one parent is the carrier?
50% and symptoms don't appear until age 40.
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Who can be gentically tested?
Embryos, children and adults
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When embryos are produced by IVF, doctors can test the embryos to check if they have got genetic disorders what is this known as?
Pre - implantation genetic diagnosis - which is especially important if one parent might be a carrier.
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When embryos are tested, which ones are chosen to be implanted into the mothers womb?
Only healthy ones - embryos with a genetic disorder are discarded.
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Why might people be tested to see if they carry alleles for genetic disorders?
Couples might want to find out if their child may inherit a particular disorder. People can also be tested prior to drug consumption - to see if the drug would be an effective treatment or if it would have an adverse affect.
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List issues of genetic testing?
Not always 100% accurate - errors due to samples getting contaminated or misinterpreted. Flase positive - healthy people being told they have a disorder. Flase negative - people being told they are healthy but they actually have a disorder.
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List issues of genetic testing?
Tests during pregnancy have a 1% chance of miscarriage. If test results are positive should others from the family be tested? Is it right to pass on a disorder to a child? Is it right to terminate the pregnancy? Discrimination against employees.
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List issues of genetic testing?
Insurance companies may refuse life insurance if they have a disorder or to people who have faulty alleles.
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What are clones?
Genetically identical organisms - same genes and alleles
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What organisms can reproduce asexually to form clones?
Bacteria, some plants and some animals
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Differences between clones must be due to what?
Their environment - e.g. if you were better nourished as a child than your clone, you would probably be taller than your clone - even though your alleles would still be identical.
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What does asexual reproduction mean?
There is only one parent and the offspring are gentically identical to each other and the parent.
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How do bacteria reproduce like this?
They divide in two.
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How do plants reproduce like this?
Some produce horizontal stems called runners, that can move out from the base of the plant and form new clones at their tips e.g. strawberry plant. Other plants produce undergound fleshy structures called bulbs e.g. garlic
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How do greenfly reproduce asexually to make identical females?
They lay eggs
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What happens when cells of an embryo splits?
These are clones
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Give an example in humans.
Identical twins are clones
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How does the embryo split?
Embryo begins to develop as normal, occasionally it splitys into two seperate embryos and they begin to develop and they are genetically identical.
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How are animal clones made?
Nucleus of an egg cell is removed leaving the egg cell without any genetic information. A nucleus from an adult donor cell is inserted in its place. The cell is then stimulated so it starts dividing. It is genetically identical to the donor cell.
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Most cells in your body are specialised for a particular job - give an example.
White blood cells are brilliant at fighting invaders but cant't carry oxygen like red blood cells.
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Cells in multicellular organisms - when do they become specialised?
Most become specialised during early development
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Some cells are unspecialised - what can they do?
They can develp into different types of cells depending on the instructions they are given. These are called stem cells.
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There are two main types of stem cell - what are they?
Embryonic and adult
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What are embryonic stem cells?
Unspecialised cells found in early embryos, they are removed from the embryo and the embryo is destroyed. Doctors and medical researchers like them. All the different types of cell found come from these in the early embryo.
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What are adult stem cells?
Unspecialised cells found in adult animals. Involved in maintaining and repairing old and damaged tissues and can specialise into many types of cell , ( but not all ). They cane safely be removed by extracting their bone marrow - no embryos destroyed
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What can stem cells be used to do?
Treat many illnesses
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Medicene already uses adult stem cells to cure disease, give an example of a disease and how to treat it.
Sickle cell anaemia. Bone marrow contains adult stem cells that can turn into new blood cells to replace faulty ones.
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Embryonic stem cells in sick people can also be used to replace faulty cells in sick people give an example.
You could make a beating heart muscle cell for people with heart disease, insulin - producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries.
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Other cards in this set

Card 2

Front

What is a gene?

Back

A code for making certain a certain type of protein, different versions of proteins means different characteristics.

Card 3

Front

Name the two types of proteins

Back

Preview of the front of card 3

Card 4

Front

Give an example of each.

Back

Preview of the front of card 4

Card 5

Front

What is genotype and phenotype?

Back

Preview of the front of card 5
View more cards

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