human heredity ch 14. human chromosomes karyotype – picture of chromosomes grouped together in...
TRANSCRIPT
Human Heredity
Ch 14
Human Chromosomes
• Karyotype – picture of chromosomes grouped together in pairs
• 23 pairs (46 total)• Two are sex chromosomes (pair #23)
– Female genotype – XX – Male genotype – XY
• Autosomes – remaining 44 chromosomes– Pair #s 1-22
• Gender of zygote is determined by male
Human Traits
• Pedigree – chart that shows relationship in family
• Used to infer genotypes of family members
Recessive alleles
• An abnormal gene shows up when an abnormal allele affects the phenotype
• Recessive – only shows up when _________
Dominant allele• Expressed even if recessive
allele present
Sex-linked genes• Only Genes located on X and
Y chromosomes• X chromosome contains more
genes being larger• Y chromosome is small so
can’t carry other traits besides the one determining the male sex characteristics
• Males MUST always express all of their X genes
• ** You can tell a trait is sex-** You can tell a trait is sex-linked if more males than linked if more males than females have it in the females have it in the population!!**population!!**
Chromosomal disorders
• Errors in meiosis• Nondisjunction -
Homologous chromosomes fail to separate
• Abnormal numbers of chromosomes in gametes
Sex chromosome disorders
• Disorders in the sex chromosomes
• May only have one X– Sterile, sex organs do not
develop at puberty• Or be a male with two X
• Presence of Y chromosome produces male sexual development no matter how many X
• Lack of Y, the embryo develops as a female
• http://www.zerobio.com/drag_gr11/sexlink.htm