Lecture 2 Flashcards
How do we inherit traits?
Genetic Inheritance…
What are genes?
Units of heredity
Part of chromosomes
Made up of pairs of alleles
What are genes made from?
DNA
What does DNA code
Synthesis of RNA
What does RNA code
Synthesis of protein
What do genes do?
Maintain structural format through generations
What are heterozygous alleles
Pairs that are different, i.e. one recessive and one dominant
What are homozygous alleles
Pairs of alleles that are the same, i.e. both recessive or both dominant
Which type of gene have the stronger effect?
Dominant gene
What are phenotypes?
Phenotypes are visible characteristics, i.e. eye colour
What are sex linked genes?
Genes on the sex chromosome (X or Y) are known as sex-linked genes
Where are the sex linked genes found?
X or Y chromosomes
Name one main difference between the X chromosome and the Y chromosome
Y chromosomes are very small - genes for only 27 proteins. X chromosomes are a lot larger - genes for 1,500 proteins
How many proteins do the X and Y chromosomes code for?
Y = 27 proteins X = 1500 proteins
Give an example of human sex-linked genes and explain
Red-Green colour deficiency.
A man with this recessive gene on his X chromosome is red-green deficient because he has no other X chromosome, yet a woman does, thus the woman will only have the deficiency if she has the recessive gene on both X chromosomes.
What are sex-limited genes?
Genes that are present in both sexes, generally on autosomal chromosomes, but active mainly in one sex.
Give examples of sex-limited genes.
Breast size
Crowing in roosters
Chest hair
Egg production in hens
Explain the difference between sex-limited genes and sex-linked genes.
A sex-linked gene is on a sex chromosome (usually the X chromosome). A sex-limited gene could be on any chromosome, but it is activated by sex hormones and therefore shows its effects in only one sex.
Suppose someone identifies a “gene” for certain aspects of sexual development. In what ways might that statement be misleading?
The effect of a gene depends on other influences. In the case of a gene affecting sexual development, the gene is probably more active during adolescence than in childhood due to sex hormones. Its effects might depend on diet, social influences and others.
How might a new species evolve?
Individuals have different traits within a population, and specific traits could be linked to higher fitness and thus these individuals will survive and reproduce. Thus the genes adapt and spread within the population by natural selection
What is the evidence for evolution?
Fossil records - species changed throughout time
Similarities of related life forms - chimpanzees share 98% DNA with humans
Rapid populations changes in organisms - artificial selections (breeding)
Geographic distributions - related species in the same island (marsupials e.g. koalas, kangaroos, opossum, marsupials are closer to each other than they are to mammals) Tasmanian wolf is closer to an anteater than to a wolf - ANALOGY
What is analogy, and give an example.
Similarities in function that evolved independently.
What is Lamarckian Inheritance?
Changes during a lifetime - offsprings inheritance
Give an example of Lamarckian Inheritance
Not using your little toe so offspring born without one
