* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 7-1 Chrom-Pheno
Ridge (biology) wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Human–animal hybrid wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Human genome wikipedia , lookup
Segmental Duplication on the Human Y Chromosome wikipedia , lookup
Genome evolution wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Behavioural genetics wikipedia , lookup
Genomic imprinting wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Gene expression programming wikipedia , lookup
Genome (book) wikipedia , lookup
Designer baby wikipedia , lookup
Microevolution wikipedia , lookup
Y chromosome wikipedia , lookup
Medical genetics wikipedia , lookup
X-inactivation wikipedia , lookup
Section 7-1 “Human genetics” Write everything that is BLACK 7.1 Human Genetics (Chromosomes and Phenotype) KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits 7.1 Human Genetics (Chromosomes and Phenotype) Two copies of each gene affect phenotype • Mendel studied autosomal (body cell) gene traits, like hair texture 7.1 Human Genetics (Chromosomes and Phenotype) • Mendel’s rules of inheritance apply to autosomal genetic disorders. – A heterozygote for a recessive disorder is a carrier – Disorders caused by dominant alleles are uncommon (dominant) 7.1 Human Genetics (Chromosomes and Phenotype) Males and females can differ in sex-linked traits • Genes on sex chromosomes are called sex-linked genes – Y chromosome genes in mammals are responsible for male characteristics – X chromosome genes in mammals affect many traits 7.1 Human Genetics (Chromosomes and Phenotype) Our chromosomes: • Recall … • In humans the diploid number of chromosomes is 46 (23 pairs) • 22 pairs of homologous (matching) chromosomes called autosomes • The 23rd pair are sex chromosomes 7.1 Human Genetics (Chromosomes and Phenotype) Sex Chromosomes: • Females are XX –Have 2 X chromosomes that are alike • Males are XY –Have 1 X and 1 Y chromosome The Y chromosome is smaller (just says be a male) 7.1 Human Genetics (Chromosomes and Phenotype) • Males have an XY genotype –All of a male’s sex-linked genes are expressed –Males have no second copies of sex-linked genes 7.1 Human Genetics (Chromosomes and Phenotype) • Females have an XX genotype – Expression of sex-linked genes is similar to autosomal genes in females – X chromosome inactivation randomly “turns off” one X chromosome 7.1 Human Genetics (Chromosomes and Phenotype) • After meiosis there are gametes (sperm or egg cells) that each have only one chromosome • All female eggs will have one X • All males will have half their sperm with X chromosomes and half with Y 7.1 Human Genetics (Chromosomes and Phenotype) •Now write everything on the next slide for your genetics book … “How a zygote is made as male or female” Female XX Eggs XX girl X X XX girl 50 % chance of a girl Male XY X XY boy Y Sperm XY boy 50% chance of a boy 7.1 Human Genetics (Chromosomes and Phenotype) Problems … • Nondisjunction: The failure of homologous chromosomes to separate properly during meiosis • This can happen in the autosomes or sex chromosomes 7.1 Human Genetics (Chromosomes and Phenotype) • If one homologous pair fails to separate, half of the sex cells produced will have one too many chromosomes while the other half has one less chromosome • Trisomy: has one too many chromosomes 7.1 Human Genetics (Chromosomes and Phenotype) • When an extra chromosome is at #21 the result is Down Syndrome • This person will have 47 chromosomes instead of 46. These are in the autosomes (not sex cells) • People with Down Syndrome usually survive, but will have mental retardation 7.1 Human Genetics (Chromosomes and Phenotype) • Monosomy: one less chromosome • These organisms usually do not survive (except in Turner’s Syndrome) 7.1 Human Genetics (Chromosomes and Phenotype) • When 2 gametes with an extra set of chromosomes fuse we it is called polyploidy • Its rare in animals and results in death • It is seen frequently in plants. Flowers and fruits tend to be bigger and plants healthier 7.1 Human Genetics (Chromosomes and Phenotype) • True hermaphrodites (both male and female organs) are very rare and are not caused by abnormal chromosome numbers 7.1 Human Genetics (Chromosomes and Phenotype) • There are many X-linked traits like: • Muscular Dystrophy, colorblindness • These are more prevalent in males because they don’t have another normal X to cover up the bad one