Genetics Flashcards

What is a gene?
A length of DNA that codes for a polypeptide
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What is a heterozygous?
A genotype where the two alleles of a gene are different
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What is a homozygous?
A genotype where the two alleles of a gene are identical
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What is codominance?
When both alleles affect the phenotype in a heterozygote
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What is the mutation for PKU?
Recessive gene mutation on chromosome 12
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What is the mutation for CF?
Recessive gene mutation on chromosome 7 in the gene for the CFTR protein. Deletion of three base pairs results in the loss of an amino acid.
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What is the mutation for Huntington's?
Autosomal dominant gene mutation on chromosome 4
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What is the result of the PKU mutation?
The enzyme phenylalanine hydroxylase is not functional so phenylalanine is not converted into tyrosine and phenylalanine builds up.This can cause brain damage
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What is the result of the Huntington's mutation?
Triplet repeat of CAG occurs 40 or more times. CAG codes for the protein huntingtons, it breaks into pieces, forming clumps, impairing or killing nuclei in the brain.
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What are the symptoms of Huntington's?
Memory loss, changes in mood and personality, uncontrolled muscle movements, difficulty speaking and swallowing, depression and anxiety
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What is the result of the CF mutation?
The CFTR protein is defective. The protein acts as a channel between the cytoplasm and surrounding fluid, responsible for the movement of chloride ions. when the protein doesn't work the chloride balance is upset. This creates a thick, sticky mucus
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What are the symptoms of CF?
Cilia can't remove the mucus and bacteria are trapped causing chronic infections that scar the lungs. Secretion of digestive enzymes is blocked so it is hard to absorb nutrients. Liver problems and infertile males.
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Describe the ABO blood groups
Determined by a protein in the cell surface membrane of RBCs. 2 forms- antigen A and B. Gene that codes for this protein has 3 alleles. Ia and Ib are codominant. Io is recessive to Ia and Ib.
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What is the mutation for SCA?
Single base substitution, uracil replacing adenine so glutamate is produced rather than valine. This affected the beta chain of Hb. HBa= normal, HBs=SCA.
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What are the symptoms of SCA?
In low Po2 the RBCs become sickle shaped and rupture. They can block capillaries, causing pain, cramps, fatigue etc.
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What is haemophilia?
A sex-linked (X chromosome) blood disease that means the blood cannot clot adequately. The dominant allele H codes for factor VIII, the recessive allele h results in a lack of the factor.
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What is autosomal linkage?
Genes that have loci close together on autosomes can be linked- they tend not be separated by crossing over during meiosis e.g nail patella syndrome and ABO blood groups.
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What is crossing over?
In prophase 1 of meiosis, the chromatids of a bivalent may break and reconnect to another chromatid. This results in the exchange of gene loci between maternal and paternal chromatids. It results in different combinations of alleles.
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What is the cross-over value?
Number of recombinant individuals produced divided by the total number of offspring times by 100.
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What can the cross-over value be used for?
To map the relative positions of genes. 2 genes with a cross-over value of 20% are said to be 20 units apart.
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What is translocation?
A chromosome mutation where a piece of chromosome breaks off and is transferred to another chromosome.
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What is non-disjunction?
A chromosome mutation where there is a change in the number of chromosomes.
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What is Turner's Syndrome?
X chromosome monosomy (XO). Symptoms include constriction of the aorta and shield-shaped thorax.
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What is Klinefelter's Syndrome?
Genotype XXY. 4 most common symptoms are sterility, breast development, incomplete masculine build and social/learning problems.
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What are the three main stages of genetic engineering?
1.Isolating and identifying the gene for the protein you want. 2.Putting the isolated gene in another organism using a vector. 3.Cloning the organism.
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How is a gene isolated?
Restriction enzymes cut the DNA at a particular sequence of bases. Some cut straight across both DNA chains (blunt ends) while others make staggered cuts (sticky ends).
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How do restriction enzymes work?
They are very specific; each one will cut DNA only at a specific base sequence, 4-8 base pairs long.
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What is the role of DNA ligase enzymes?
The repair the DNA backbone by forming covalent bonds; it links up the sugar-phosphate backbones of the newly paired section.
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What is a bacterial plasmid?
A small, circular strand of DNA found in bacteria in addition to their main DNA. They are often used as vectors that transport the DNA into the host cell.
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What are marker genes?
Genes that express readily observed characteristics. They are inserted into the recombinant DNA that will be transferred to the vector. If the DNA is taken up the marker gene will express itself-tell which organisms have been successfully engineered
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What is the use of complementary DNA?
cDNA is DNA copied from mRNA. The enzyme reverse transcriptase synthesizes DNA from an RNA template. The enzyme is a retrovirus. The DNA made is single-stranded but DNA polymerase can be used to produce a double stranded cDNA.
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What are the advantages and disadvantages of using microorganisms in genetic engineering?
They are easy, quick and cheap to culture and there are few ethical issues. They cannot make all human proteins e.g glycoproteins.
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How are proteins extracted from plants or animals?
Plants- secreted from roots or cultured by protoplasts. Animals- secreted in milk or urine.
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What is gel electrophoresis?
A form of chromatography used to separate different pieces of DNA on the basis of their length.
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How is gel electrophoresis carried out?
Samples of DNA are placed in holes at the end of the gel,electric current passed through gel making strands move. Shortest move furthest, strands of same length group together, stain added
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What is the Polymerase Chain Reaction?
A way of replicating DNA in a test tube. High temperatures are used to separate the DNA molecules into single strands, this breaks H bonds so the DNA unzips. The DNA is cooled then added to activated nucleotides and DNA polymerase. CBP occurs.
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What is DNA profiling?
A form of genetic fingerprinting. Uses both PCR and gel electrophoresis. It identifies patterns of genetic material, exploiting minisatellites.
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What are minisatellites?
A section of DNA made up of repeated sequences. The number of copies varies between individuals.
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What is gene therapy?
An experimental technique that uses genes to treat or prevent disease. Techniques include inserting a normal gene to replace an abnormal one, repairing abnormal genes or altering the degree to which a gene is turned on or off.
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What are the problems with gene therapy?
Short-lived nature of recombinant DNA. Immune response could be triggered. Problems with viral vectors as they could cause a disease. Multigene disorders would be very hard to treat.
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What is the difference between somatic and germ cell therapy?
Somatic involves adding genes to cells other than egg or sperm cells. Germ involves changing genes in eggs, sperm or early embryos.
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What is the Human Genome Project?
A project devised to map and sequence the entire human genome- locate every gene on every human chromosome. It has led to the discovery of 1800 disease genes, biotechnology products and genetic tests.
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What is the role of pedigree charts?
Show inheritance patterns of genetic conditions. They can predict the likelihood of a child being born with a genetic disease.
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What is the point of genetic engineering?
Helps people understand the nature of a disease and the risk they have of passing it on, what options are available to them and how the disease could influence family life.
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What is genetic compatibility?
The degree of genetic similarity at a particular locus between the individuals. First they see if they are the same blood group then they carry out tissue typing.
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What are the HLA and MHC?
The gene that codes for the HLA is found on chromosome 6 and there are 6 gene loci. This area of C6 is called the MHC. The loci are close so tend to be inherited together. Each set of HLA antigens is a haplotype, you inherit one from each parent.
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What HLA matches are important?
Solid organs- HLA-A, B and DR antigens. Bone marrow/stem cells- HLA-A, B, C, DR, DP, DQ.
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What are the sources of donated organs?
Cadavers, living donors, xenotransplantation (animal-human)
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What are the benefits and problems associated with the sources of organ donations?
Cadavers-help relatives cope, no harm being done, multiple organs. Hard to ask relatives, number is falling. Living Donors- better outcomes, reduced waiting time. Risk to donor. Animals- solves shortage. Rejection, diseases.
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Where are embryonic stem cells found?
In a blastocyst. Blastocysts may be left over after IVF or they can clone embryos and harvest stem cells from them.
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Why are embryonic stem cells needed?
Tissue transplants, possibly organ transplants, testing drugs, 'designer babies'.
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What is the difference between therapeutic and reproductive cloning?
Therapeutic involves treating disease and disability, it is legal in the UK. Reproductive looks at cloning human embryos to create a baby, it is illegal.
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What are the ethical considerations of cloning and transplants?
All embryos have the potential to be a full human, destroying them is killing a life. Safety concerns. Lead to a new eugenics, designer babies. Only the rich may have access, creating classes. T-shortage, opt in or out, sale of organs?, brain dead?
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Other cards in this set

Card 2


What is a heterozygous?


A genotype where the two alleles of a gene are different

Card 3


What is a homozygous?


Preview of the front of card 3

Card 4


What is codominance?


Preview of the front of card 4

Card 5


What is the mutation for PKU?


Preview of the front of card 5
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