1 2 Heritability Study Questions Ashlyn Molinaro 1 What is heritability how do we study it what are twin and adoption studies what do their results tell us and what are the problems with studying it Heritability is when variations in some characteristics depend largely on genetic differences We study it through virtual twin studies adoption stories unrelated children adopted very young at the same age and raised together and twin studies In twin studies we compare monozygotic twins from one egg and dizygotic from two eggs Monozygotic identical twins even though this term may be misleading Mono twins have the same genes where as Di do not A stronger resemblance between MZ than DZ suggests a stronger genetic contribution With virtual twins any similarities can be attributed to environmental Behavioral differences can suggest genetic influences Third kind of evidence identify specific genes linked to behavior Problems Sometimes differences may be due to prenatal environment 2 What are examples of environmental influences on traits with otherwise high heritability An example is Phenylketonuria or PKU which is a genetic inability to metabolize amino acid phenylalanine If it is not treated the kids become mentally retarded Environmental intervention can modify it We put the kids on a strict diet and this minimizes brain damage This provides strong evidence that heritable does not mean unmoldable 3 What is a sex linked gene Understand the heritability of sex linked genes What is a sex limited gene What are examples of each sex linked and sex limited A sex linked gene is the gene on the sex chromosome designated X and Y All others are autosomal chromosomes and their genes are known as autosomal genes contributes an X chromosome and the male gives either an X or a Y If he gives an X it s a girl If he gives a Y it s a boy Man determines gender Sex limited genes Present in both sexes but active mainly in one sex Examples are the genes that control breast size in women or Heritability of them Females are XX Males are XY The female 1 2 Heritability Study Questions Ashlyn Molinaro chest hair in men Both sexes have them but sex hormones activate them in one sex or the other Boys are more likely to express a sex linked trait because if the trait is on the x they don t have another x to recompense Girls however will be carriers if they have the mutilated x but their other x will not let the trait show 4 Terms to know and understand DNA RNA gene chromosome transcription translation allele homozygous heterozygous dominant recessive DNA Deoxyribonucleic acid Double stranded molecule A model template for the synthesis of RNA Contains four bases adenine guanine cytosine and thymine The two that connect are adenine and thymine guanine and cytosine RNA Ribonucleic acid A single strand chemical One type of RNA molecule serves as a template for the synthesis of protein molecules They have the same bases as DNA except instead of thymine they have uracil Gene Units of heredity that maintain their structural identity from one generation to another AKA a sequence of DNA Chromosome Strands of genes Genes are aligned along chromosomes because they are both in pairs Contains DNA Transcription When information in the DNA is copied into the messenger RNA for protein production The process of making RNA from DNA by copying one strand of the DNA Translation Ribosomes reads the mRNA and translates it into the amino acid sequence of the protein Process of making proteins from RNA Allele pairs or series of genes on a chromosome that determine the hereditary characteristics Homozygous anyone with an identical pair of genes on the two chromosomes is homozygous for that gene Two of the same Alleles Heterozygous An individual with an unmatched pair of genes is heterozygous for that gene Two different alleles 1 2 Heritability Study Questions Ashlyn Molinaro Dominant Gene that shows a strong effect in either the homozygous or heterozygous condition Recessive Gene that shows strong affect only in homozygous condition So you need two copies of that gene to see that trait 5 How is it that genes can affect behavior Genes alter neurotransmitters and other chemicals resulting in how an individual processes information perceives stimuli and responds to their environment responds to the individual Also altering physical appearance and how the environment 6 Understand the concept of epigenetics and why this blurs the line between nature and nurture Know the examples of epigenetic changes we discussed Epigenetics deals with changes in gene expression without EX rats mom is malnourished during pregnancy offspring modification of the DNA sequence Although a gene is present it might not be active in all cells or only active at one point in life such as embryonic development Some genes are more active in puberty some less in old age Some more active different times of day alters expression of certain genes to conserve energy and live in a world with not much food If rich food appears in life offspring predisposed to high probability of obesity because of gene expression Blurs line because the reason someone is how they are may be genetics or could be due to their prenatal environment Examples Changes in brain resulting from drug addiction 7 Although we did not discuss it be sure to read the section in your book on the evolution of behavior and evolutionary psychology p14 18 in 11th ed Evolution is a change over generations in the frequencies of various genes in a population
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