IB Biology: Genetics

32 flashcards · Other · by Gabrielle Wong

1. Gene: A heritable factor that consists of a length of DNA and influences a specific characteristic in an organism.

   The specific location of a gene on a chromosome is called a loci Homologous chromosomes will have the same genes, but may not have the same alleles

2. Chromosome: structure that contains condensed DNA associated with histone proteins

   There are 23 pairs of chromosomes in humans. Each pair has two homologous chromosomes.

3. Allele: specific variation of a gene

   Homologous chromosomes will have the same genes, but may not have the same alleles

4. Mutation: A change in the DNA sequence in an organism. This may or may not cause a change in the structure of proteins.

   2 factors that may increase risk of mutation: Chemicals, specifically length of exposure to them. Chemcials increase the mitotic index, leading to a higher percentage of error, plus chemicals can breakdown DNA Radiation, which may modify the DNA code by knocking bases out of place

5. Genome: the whole of genetic info of an organism requires sequencing of DNA different organisms will have different genome sizes

   The Human Genome Project (1990-2003) determined the entire human genome, and is now working on interpreting those sequences. As a result, DNA cn be used to make medicine by taking advantage of naturally beneficial molecules. Also has led to greater development of biotech

6. Diploid: contains two sets of chromosomes (making 23 homologous pairs)

   Mitosis produces 2 diploid cells that are genetically identical.

7. Haploid: single set of chromosomes, seen in gametes

   Meiosis produces 4 haploid cells that are genetically diverse

8. Karyogram: A picture of the chromosomes found in a cell, arranged in homologous pairs from large to small.

   Karyograms are found by karyotyping.

9. Sex chromosomes: the twenty-third pair, responsible for determining sex

   XX = female XY = male

10. Autosomes: chromosomes that don't determine sex

    Humans have 44 of these (22 pairs)

11. Meiosis: process that leads to the production of gametes Meiosis I Prophase: chromosomes condense, formation of spindle, homologous chromosomes pair, crossing over occurs Metphase: microtubules tug homologous chromosomes to equator, independent assortment occurs Anaphase: spindle fibres retract, homologous chromosomes are separated Telophase: spindle disintegartes, reformation of the nuclear membrane, chromosomes may decondense before meiosis II

    Has two stages, but meiosis II is very similar to mitosis

12. Crossing over: Trading of sections of DNA between homologous chromosomes , leading to genetic variation

    Crossing over occurs during prophase I

13. Non-disjunction: when homologous chromosomes fail to separate

    Non-disjunction in the 21st pair of homologous chromosomes causes Down Syndrome

14. Genotype: alleles of an organism Pheontype: actual traits of an organism Carrier: heterozygous (different), has recessive trait but does not express it Purebred: homozygous (same) Test cross: cross with a recessive to determine genotype (only hetereozygous will result in recessive offspring) Dominant trait: can appear in heterozgous or homozygous form Recessive trait: can appear only in homozygous form

    This is vocab related to inheritance and Mendel genetics

15. Co-dominance: occurs when the traits of both alleles are expressed

    Example: Red fish, blue fish, red and blue fish

16. Incomplete dominance: occurs when the traits of alleles combine, leading to a different trait

    Example: Red fish, blue fish, purple fish

17. Multiple alleles: when many different alleles control a characteristic

    Example: Blood type

18. Sex-linked traits: traits whose genes are found only on the Y or only on the X chromosome

    Example: Colour blindness, hemophilia

19. Down syndrome: condition caused by having 3 chromosome 21s, which is caused by non-disjunction

    Consequences of Down Syndrome include flat facial features, atypical ears, poor muscle tone, eyes that slant upwards, and intellectual/developmental delay

20. Huntington's: autosomal dominant disease, a type of progressive brain disorder

    Consequences of Huntington's include uncontrolled movement, poor co-ordination, slurred speech, irritability, trouble with learning and decision making

21. Sickle cell disease: caused by a mutation in which a base substitution leads to the production of glutamic acid instead of valine

    Consequences of Sickle Cell include: blood cells form a sickle shape and are unable to carry oxygen as well, leading to fatigue, shortness of breath, blocked blood flow, but may also increase resistance to malaria

22. Cystic Fibrosis: caused by the deletion of three bases on the 7th chromosome, leading to the removal of phenylalinine

    Consequences of Cystic Fibrosis include: excessive mucus produciton, frequent lung infections, and salty tasting skin, but may provide resistance to cholera and dehydration

23. Parental screening: requires the obtaining of fetal cells for karyotyping Amniocentesis: removal of fluid that contains fetal, then chemicals are applied to increase the rate of mitosis and then stop the cells in metaphase so karyotyping can occur Chorionic villus sampling: cells are taken from projections of the placenta in the uterus

    Parental screening can detect certain genetic conditions ex. Huntington's, Down Syndrome

24. Theraputic Cloning Removal of nucleus from an unfertilized egg Donor (non-gamete cell) is cultured Nucleus and the unfertilized egg are fused with electrical current In-vitro fertilization Embryo is placed in surrogate mother

    First animal to be cloned: Dolly the Sheep

25. DNA Profiling: used to match DNA samples requires gel electrophoresis to separate DNA bands looking for similarities; indicates similar genetic background

    Uses: paternity suits ecosystem studies forensics

26. PCR: stands for polymerase chain reaction DNA is denatured primers are prepared Taq DNA polymerase pairs with completementary base pairing

    Uses: making copies of DNA to insert into organisms part of DNA profiling, especially with an initial small sample

27. Gel electrophoresis: used to separate DNA by size Salt water and agarose gel are placed in contained with a power supply (conduction of electricity) Stained DNA fragments are loaded into gel DNA phosphate: DNA will move towards positive pole Smaller DNA fragments move faster and farther Samples can then be compared

    Uses: identifying individuals and genetic relationships identifying DNA fragments separation of DNA fragments

28. Gene sequencing: process of determining the sequence of bases Polymerase adds complementary pairs and random chain terminators with radioactive form of a base Gel electrophoresis splits endings, which are a known base, allowing information to be filled in

    Uses: Human Genome Project figure out sequence of DNA in an organism and therefore potential use

29. Restriction Endonuclease: recognizes a certain DNA seuence and breaks the DNA apart by catalyzing the hydrolysis of bonds between the DNA

    Often used in conjunction with DNA ligase for gene transfer

30. DNA Ligase: DNA must have matching ends, ligase uses ATP to catalyze formation of bonds

    Often used in conjunction with restriction endonuclease for gene transfer

31. Gene transfer/splicing: moving genes from one organism to another

    Uses: gene splicing to modify DNA creation of GMOs ex. BT plants modified with a protein that is toxic to pests repairing DNA breaking apart DNA for analysis

32. Cairns' Technique: a form of autoradiography (A technique of exposing photographic film using radioactive markers that have been embedded in the sample themselves (as opposed to passing x-rays through the sample). Use in looking at DNA) DNA is given radioactive thymidine (radioactive marker) Form will keep track of the molecule's size and shape leaves markings on the film after development

    Uses: demonstrating that the chromosome of prokaryotes is circular