Inheritance Flashcards
What is a gene?
A section of a molecule of DNA that codes for a specific protein
Describe a DNA molecule
Two strands coiled to form a double helix, the strands are linked by a series of paired bases: adenine (A) with thymine (T), and cytosine (C) with guanine (G)
What are alleles?
Different forms of a gene which gives rise to differences in inherited characteristics
Describe the meaning of the terms: dominant, recessive, homozygous, heterozygous, phenotype, genotype and codominance
Dominant: one that will be made because it is ‘dominating’ against the recessive allele
Recessive: only shows if the individual has two copies of the recessive allele.
Homozygous: two copies of one allele
Hetrozygous: a copy of two alleles
Genotype: the alleles each cell has
Phenotype: the feature that results from the genotype
Describe the process of mitosis
Chromosomes are copied as the DNA replicates and more histones are made. Parent cell has two homologous pairs. Two chromatids make up each chromosome; they are joined by centromere. A spindle forms and the chromatids attach to it. The spindle fibres shorten and pull the chromatids of each chromosome to opposite poles of the cell. Two new nuclei form at the poles of each cell, each has a copy of each chromosome from the parent.
Describe the process of meiosis
DNA is duplicated and forms two chromatids. The pairs are pulled apart by spindle fibres so that one chromosome from each homologous pair is in each daughter cell. The chromatids are separated and one chromatid from each chromosome ends up in each daughter cell as the arm of the chromatids are pulled apart.
What is random fertilisation?
When Two Sex Cells Combine to Form a New Diploid Cell (Zygote) at Fertilisation, this Results in Genetic Variation of the Offspring
This is because the Variation of the Sex Cells (Gametes) are Increased in Variation themselves as a Result of Meiosis
Variation is Further Increased as the Fusing of the Egg and Sperm is Random, Causing Every Human Being to be Genetically Different from Each Other (Except for Twins who are Formed from the Same Zygote)
What is a mutation?
A rare, random change in genetic material that can be inherited
Describe the process of evolution by means of natural selection
A mutated organism will be better adapted to survive in the environment. They will have an increased chance of breeding, passing on their better genes. Over many generations, species will become better at surviving. The ‘best’ features are naturally selected and so the species become better adapted to their environment.
How can resistance to antibiotics increase bacterial populations?
Bacteria can develop random mutations, which can change their characteristics.
It’s an advantage for bacteria to resist antibiotics, as it’s able to survive better and live longer, as well as reproduce many more times.
It leads to the gene of resistance being passed on to offspring (natural selection, meaning that this gene eventually becomes more common in the bacteria population).
This becomes a problem for people infected with these bacteria, as they’re hard to get rid of with antibiotics. Sometimes, drug companies may come up with a newer antibiotic that’s more effective, however ‘superbugs’ that are resistant to most known antibiotics (e.g. MRSA), are becoming more common.
How can the incidence of mutations be increased?
Can be increased by exposure to ionising radiation and some chemical mutagens (chemicals in tobacco).
