* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Lecture #3 Sex Linked Traits
Survey
Document related concepts
Causes of transsexuality wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Gene expression programming wikipedia , lookup
Sexual dimorphism wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Microevolution wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Genomic imprinting wikipedia , lookup
Designer baby wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Genome (book) wikipedia , lookup
Neocentromere wikipedia , lookup
Y chromosome wikipedia , lookup
Transcript
Lecture #3 Sex Linked Traits Unit: Mendelian Genetics Refresher from last Quarter The complete human genome consists of 46 chromosomes. 23 of these chromosomes come from ‘mom’ (egg) and the other 23 chromosomes come from ‘dad’(sperm). Only 2 of those 46 chromosomes determine an individuals sex and are referred to as the SEX CHROMSOMES. The other 44 are referred to as AUTOSOMES. Sex Chromosomes Two varieties of SEX CHROMSOMES: X & Y – Females have two copies of the X chromosome. (XX) – Males have one X chromosome and one Y chromosome. (XY) ** Males determine the sex of a baby because females have only an ‘X’ to give to each egg. Sperm contains either an ‘X’ or a ‘Y’ (50:50 chance of either) Sex Chromosomes – This Punnett square illustrates why males and females are born in a roughly 50 : 50 ratio. Sex-Linked Inheritance – A sex-linked gene is a gene located on a sex chromosome – Genes on the Y chromosome are found only in males and are passed directly from father to son. – Genes located on the X chromosome are found in both sexes, but the fact that men have just one X chromosome leads to some interesting consequences. Sex Linked Traits – More than 1200 genes are found on the X chromosome – The human Y chromosome is much smaller than the X & contains only about 140 genes, most of which are associated with male sex determination and sperm development. Examples of sex-linked disorders • • • • Hemophilia ( bleeders disease) Color blindness Muscular dystrophy Spotted coat coloring in cats Sex-Linked Inheritance Most sex-linked traits are recessive Males exhibit sex-linked disorders more often. Why? • The sex-linked trait is on the X chromosome. Males only have one copy of the X chromosome. If they have 1 copy of the recessive allele that causes the disorder, they will have the disorder Red Green Color Blindness is the most common type Male Red-Green Color Blindness: 1 in 12 Female Red-Green Color Blindness: 1in 200 Females: need 2 copies of the recessive allele in order to exhibit (have) the condition. This makes the chances of the female exhibiting the condition significantly less. Carrier- an individual who is heterozygous for an inherited disorder, but does not show symptoms of the disorder. • Female can be carriers for sex-linked disorders and pass on the recessive allele to her offspring however. • If she were to have a colorblind son, where did the recessive allele come from? Mom? Dad? Is it possible to tell? Answer: Its mom’s fault! Explanation- Dad gave the son his “y” (that is why the child is a male!), mom gave the X, which contained the recessive allele for colorblindness. Take 2 minutes to summarize what you have learned regarding the inheritance patterns of sex linked traits.