4.3 - Inheritance Flashcards
Define what an allele is
A version of a gene that occurs at the same locus on homologous chromosomes
What is autosomal linkage?
When two or more genes are positioned on the same autosome. They are unlikely to be separated by crossing over during meiosis so are often inherited together
Define autosome
A chromosome that is not an X or a Y chromosome
Explain what carcinogen is
A type of mutagen that causes cancer
What is the Chi-squared test?
A statistical test used to determine whether a pattern of inheritance is statistically significant
What is chromosome mutation?
A change in the structure or number of chromosomes. This affects many genes
What is co-dominance?
When both alleles for a gene in a heterozygous organism equally contribute to the phenotype
What is the degrees of freedom (X2 test)?
The number of categories minus one
What is the dihybrid mandelian inheritance?
The determination of a trait by the inheritance of two genes
Define the meaning of dominant
Describes an allele that is always expressed. Represented by a capital letter
Explain what Down’s syndrome is
A genetic disorder characterised by delayed development and learning disabilities. Due to non-disjunction, an affected individual possesses three copies of chromosome 21
What is Duchenne muscular dystrophy (DMD)?
An X-linked recessive condition characterised by muscle degeneration and weakness. It is more common among males because they only inherit one X chromosome.
Define what epigenetics are
The study of changes in gene expression that are not due to alterations in the nucleotide base sequence of DNA
What is F1 generation?
The first generation of offspring resulting from the cross of two individuals in the parental generation
What is F2 generation?
The second generation of offspring resulting from the cross of two individuals in the F1 generation
Explain what a gene is
A length of DNA on a chromosome that codes for the production of one or more polypeptide chains and functional RNA
What is gene mutation?
A change to at least one nucleotide base in DNA or the arrangement of bases. Gene mutations can occur spontaneously during DNA replication and may be beneficial, damaging or neutral
Define what a genotype is
An organism’s genetic composition. Describes all alleles
What is haemphilia?
An X-linked recessive condition that results in excessive bleeding and blood that is slow to clot. It is more common among males because they only inherit one X chromosome
Define what heterozygous means
When someone has two different alleles of a gene e.g. Ff
What is histone modification?
The alteration of histones by the addition of methyl, acetyl, or phosphate groups. This can increase or decrease gene expression by making the DNA more or less accessible to transcription factors
Define what homozygous means
When someone has two identical alleles of a gene e.g. ff
Explain what locus means
The position of a gene on a chromosome
What is methylation?
The transfer of methyl groups to cytosine bases of DNA. Methylation inhibits transcription by making the DNA less accessible to transcription factors or preventing transcription factors from binding. This deactivates the gene
What is monohybrid mendalian inheritance?
The determination of a trait by the inheritance of a single gene
Define what a mutagen is
A chemical, biological or physical agent that increases the rate of gene mutations above normal level
What is non-disjunction?
The failure of homologous chromosomes to separate in anaphase I or sister chromatids to separate in anaphase II, resulting in a change in the diploid number of chromosomes
What is oncogene?
Mutations of proto-oncogenes that are activated continuously, resulting in uncontrolled cell division
What is a phenotype?
An organism’s observable characteristics. Due to interactions of the genotype and the environment
Explain what recessive means
Describes an allele that is only expressed in the absence of a dominant allele. Represented by a small letter
What is a sex chromosome?
A chromosome that determines the sex of an organism. e.g X and Y chromosomes in humans and other mammals
What does sex-linkage mean?
The inheritance of a gene only present on the X chromosome in organisms with X and Y chromosomes. This is due to many gene loci on the X chromosome having no counterpart on the Y chromosome
What is the sickle cell anaemia?
A recessive genetic disorder caused by a substitution mutation on chromosome 11. This results in abnormal haemoglobin which distorts red blood cells
