Chapter 15 - Chapter 15 The Chromosomal Basis of...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 15: The Chromosomal Basis of Inheritance The Basis of Gender:  The  X   chromosome and the  Y  chromosome The genotype of a male: XY The genotype of a female: XX Female Genotype Male Genotype Do a Punnett Square cross to determine the probability that a couple’s next child will be a male: 1 of 14
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Sex-linked genes The X and Y chromosomes are considered a homologous pair, however, they are not particularly homologous. Some genes on  the X chromosome have no counterpart on the Y chromosome and vice versa.                                     X Y X and Y are  chromosomes.  They contain hundreds or thousands of genes, many of which are unrelated to gender.  Since the X chromosome is much larger than the Y chromosome, the Y chromosome lacks many genes found on the X chromosome. Sex-linked traits are recessive.  The 3 major sex-linked (in fact, X-linked) traits are: male pattern baldness color blindness hemophilia 2 of 14
Background image of page 2
Do a Punnett Square cross to determine the percentage and gender of the following couple’s  offspring that will be  hemophiliacs: A heterozygous woman carrying the recessive allele for hemophilia marries a man who is not a hemophiliac.  Let  H  represent the allele  for normal clotting factors.   What is the woman’s genotype:    X H   X H ,     X H  X h ,    or    X h  X h What is her husband’s genotype: X H  Y,    X h  Y,    X H  Y H ,    X H  Y h         X _    Y_    X _    X_ What is the probability that their next child will be a hemophiliac?   ______________ Patterns of Transmission in Sex-Linked Traits 3 of 14
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 of 14
Background image of page 4
Linked genes and linkage mapping Genes located on the same chromosome tend to be passed along as a unit and are called  linked genes . But the results  obtained from breeding experiments with fruit flies (Drosophila melanogaster) deviate from the results expected according to  Mendel’s Law of Independent Assortment. How do we account for these unexpected results?   5 of 14
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Crossing over during meiosis produces recombinant chromosomes (recombinants). The frequency of recombination reflects  the distance between genes on the same chromosome. A map showing the location of alleles along a single chromosome is called a  linkage map . The distance between alleles is measured in map units. One map unit is equivalent to a 1% recombination frequency. Errors in Meiosis
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/07/2008 for the course BIO 101 taught by Professor Stein during the Spring '07 term at South Carolina.

Page1 / 14

Chapter 15 - Chapter 15 The Chromosomal Basis of...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online