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Inheritance
Fichas del conjunto (36)
- 1What is a gene?A sequence of DNA that codes for a polypeptide and occupies a specific locus on a chromosome
- 2What is an allele?An alternative form of a gene
- 3What is meant by homozygous?Both alleles of a gene are the same
- 4What is meant by heterozygous?Each allele of a gene is different
- 5GenotypeThe genetic make-up of an individual
- 6PhenotypeA characteristic expressed from a genotype
- 7What is meant by dominant?The allele which is always expressed in a phenotype
- 8What is meant by recessive?A characteristic only expressed when it is homozygous
- 9What is monohybrid inheritance?The inheritance of a single gene (e.g. seed colour or plant height)
- 10What is a test cross?Cross between an individual with the phenotype of a dominant characteristic, but unknown genotype, with an individual who is homozygous recessive for the gene in question
- 11What is co-dominance?When both alleles in a heterozygote are expressed individually. (E.g. AB blood group- expressed as IAIB, and speckled hens having black and white coloured feathers)
- 12What is incomplete dominance?When the phenotype of a heterozygote is intermediate between the two parental phenotypes (E.g. Red and white carnations make pink carnations)
- 13What is dihybrid inheritance?The simultaneous inheritance of two unlinked genes (genes on different chromosomes)
- 14What is linkage?The alleles of two genes that are on the same chromosome and cannot segregate independently.
- 15How can linked genes be recognised?Numbers of progeny with different combinations of characteristics do not correspond to Mendelian ratios (9:3:3:1)
- 16What are autosomes?In humans, there are 22 autosomes which are homologous pairs with identical genes.
- 17What are heterosomes?Chromosome pairs with different size chromosomes. In humans, the 23rd pair are the sex chromosomes. In men, they are X and Y chromosomes where the Y chromosome is much shorter.
- 18What is sex linkage?A gene is carried by a sex chromosome so that a characteristic it encodes is seen predominantly in one sex
- 19Name a sex-linked conditionDuchenne muscular dystrophy, Haemophillia
- 20How does sex-linkage work?When a recessive allele occurs on the X chromosome of males, it is expressed because the Y chromosome does not carry a corresponding dominant allele. Females however, have 2 X chromosomes so they must have 2 recessive alleles for the characteristic to appear
- 21What is a Gene (point) mutation?DNA is not copied accurately in S phase before cell division.
Addition- A base is added. If 3 is added, an extra amino acid is added to the polypeptide chain
Duplication- the same base is added twice
Subtraction- A base is deleted
Substitution- a different base is incorporated
Inversion- Adjacent bases on the same DNA strand exchange position - 22What are the different types of mutation?Gene or point mutation, chromosome mutation, aneuploidy and polyploidy
- 23What is a Gene or point mutation?DNA is not copied accurately in the S phase, before cell division.
Addition- A base is added - 24What is a chromosome mutation?Chromosomes can get damaged and break. They may not repair correctly, altering their structure and potentially altering a large number of genes
- 25What is aneuploidy?A whole chromosome may be lost or added by non-disjunction, where chromosomes fail to separate to the poles of dividing cells at anaphase I or chromatids fail to separate at anaphase II
- 26What is polyploidy?The number of chromosomes may double if the cell fails to divide following the first nuclear division after fertilisation.
- 27What is a silent mutation?In a gene mutation, the new codon produced may code for the same amino acid so there is no change in the polypeptide chain
- 28What is sickle cell anemia?A substitution point mutation in the gene producing the B-polypeptide of haemoglobin. This causes the cell membrane of the red blood cell to collapse
- 29What is Down's syndrome?An aneuploidy mutation, where chromosome 21 either has no chromosome or 2 copies instead of 1. A secondary oocyte with 2 copies of chromosome 1 fuses with a sperm to produce 3 copies of chromosome 21. This causes Down's syndrome.
- 30What is a carcinogen?An agent that causes cancer and can cause mutation in DNA
- 31What are tumour suppressor genes?Genes that regulate mitosis and prevent cells dividing too quickly. If a mutation occurs in a tumour suppressor gene to make it lose its function, a cell could go through continual, repeated mitosis, causing a tumour.
- 32What makes a tumour malignant?A tumour that's able to spread around the body and invade other tissues causing secondary tumours
- 33What are proto-oncogenes and oncogenes?A proto-oncogene codes for a protein that contributes to cell division. Mutation may switch this protein on permanently, causing rapid, repeated mitosis i.e. cancer. When a proto-oncogene is mutated such that it causes cancer, it is called an oncogene.
- 34How does an oncogene occur?When a mutation causes chromosomes to rearrange, ad places the proto-oncogene next to a DNA sequence that permanently activates it.
There is an extra copy of the proto-oncogene, resulting in too much of its product being produced, causing excessive mitosis - 35What is epigenetics?The control of gene expression by modifying DNA or histones but not by affecting the DNA nucleotide sequence
- 36What types of epigenetic modifications are there?DNA Methylation- A methyl group is added to the bases of DNA. If regions of DNA is heavily methylated, it is less likely to be transcribed
Histone modification- attatching an acetyl/methyl/phosphate group to amino acids. This changes the interaction of histones with the DNA. This causes the coiling of DNA to relax, so RNA polymerase has more access to DNA. Transcription is increased.
Información
- Descripción
- Flashcards on genetic inheritance A level Biology
- Creado por
- Seren Jones
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