Presentation on theme: "Inheritance, Pedigrees, Karyotypes, Punnett Squares Find this information in your text: genes on chromosomespage 350 pedigrees pp 342-343 karyotypes p."— Presentation transcript:
Inheritance, Pedigrees, Karyotypes, Punnett Squares Find this information in your text: genes on chromosomespage 350 pedigrees pp karyotypes p 341 dominant & recessive alleles & what causes the loss of function in proteins coded by recessive allelespp and pp Punnett Squares p 268
Humans reproduce sexually. This means females produce eggs (ova) carrying only one of each chromosometotal 23, while males produce sperm carrying only one of eachtotal 23. When sperm and egg unite at fertilization, a zygote with a full double set of chromosomestotal 46is formed.
Its random which set of your 23 homologous chromosomes youll sort (by cell division called meiosis) to each gamete. This drawing (organism w/ 2 kinds of chromosomes) shows 2 n combinations of chromosomes possible (n=# different types chromosomes)in gametes (sperm or eggs) or about 8 million possible ways exist to sort your two sets of 23 chromosomes into gametes!
Meiosis is a type of cell division that results in your giving one of each chromosome to your child in a sex cell, sperm or egg. Having one copy of each chromosome is called haploid.
LE 14-4 Because offspring have 2 of each type of chromosome, they have 2 copies of each gene. Offspring may receive identical versions of the gene (alleles) from both parents and be homozygotes OR they may receive different alleles from the two parents and become heterozygotes. Allele for purple flowers Homologous pair of chromosomes Allele for white flowers Locus for flower-color gene
A map of the human X chromosome showing that it always carries the same genes in the same order. The smaller Y is lacking most of these genes, so boys more commonly inherit recessive diseases associated with these diseases (called sex linked diseases)
Metaphase karyotype --colchicine used to trap cells at max condensation during metaphase of mitosis. Human body cells are diploid with 2n = 46. Why? Body cells are produced by asexual mitotic division. Human gametes are haploid with 1n = 23. Why? Gametes are produced by sexual meiotic cell division.
Genes carry out the jobs of a cell. If critical jobs are done by a protein, then mutations that alter its function can cause genetic disorders. Diabetesno insulin made (recessive) Tay Sachs –no brain lipid digesting enzyme made (recessive) Dwarfismno growth factor made (recessive) Albinismno pigment for skin, hair, eyes made (recessive) Cystic fibrosisno salt channel made to allow ions of salt to escape cells recessive antennepialegs instead of antennasautosomal dominant! Colorblindness, boy in a bubble suit disease, hemophiliasex linked recessive on the X csome in humans Huntingtons diseasetoo much huntington proteinautosomal dominant, late onset, one of a few dominant and common inherited disease Inherited breast cancerBRCA genes inactiveno tumor suppressors autosomal dominant Certain inherited leukemiastranslocation makes cell cycle control genes too active and too abundantdominant autosomal.
Wwww Ww wwWwww Ww WW ww or Ww No widows peak Third generation (two sisters) Recessive Trait: No Widows peak Second generation (parents plus aunts and uncles) First generation (grandparents) Dominant trait (widows peak) Pedigrees are family trees showing whether each person does (filled in) or does not (not filled in) have a particular trait. Males are shown as & females as O.
Cleopatra (Queen of Egypt, descended of the Pharoahs). Since Pharoahs were considered god-like, they were only able to marry people of the same status.
2/17/2010, King Tuts 5 generation pedigree was published (DNA tests of blood cells in mummies) Tuts parents were brother and sister, and Tut was married to his sister. King Tut had several obvious disorders, likely due to double doses of recessive alleles from his brother/sister parents: Cleft palate, club foot, severe scoliosis, other bone disease Tuts own two children were still-born.
LE 14-14b First generation (grandparents) Ff FF or Ffff Ff ff Ff Second generation (parents plus aunts and uncles) Third generation (two sisters) Attached earlobe Free earlobe ffFF or Ff Recessive trait (attached earlobe)
Pedigree for a disease caused by a recessive allele. Note that marrying a relative increases changes of inheriting 2 recessive alleles.
Pedigree for a disease caused by a dominant allele. No carriers! One disease causing allele makes you sick.
Geneticists use pedigrees to locate relatives who are healthy versus ill due to inherited disease. Comparing their data allows the defective gene to be identified.
Construct pedigrees for your own familys trait data. Use the pedigree to determine as many genotypes (the 2 forms of the alleles) as possible. Widows peakdominantcolor symbol if person has widows peak ww -no widows peakWw or WW -has widows peak Attached earloberecessivecolor person with attached earlobes EE or Ee-free earlobeee-attached earlobe Hitchhikers thumbrecessivecolor person who can bend thumb all the way; half color (a carrier) a person who can bend it a little HH-stiff thumb (no bend)Hh -bends a little hh-up to a 90 degree backwards thumb! Tongue rollingdominantcolor person who can roll tongue TT or Tt-can roll tonguett -cant roll tongue Curly hairdominantcleft chin--dominant Freckles--dominantNo hair on finger middle bondrecessive Right over left thumb/hand-recessivebent pinky-dominant
Punnett Squares allow you to predict all the possible combinations of gene alleles that mates might pass to children. Here is an example for a father having one A and one a allele and a mother having one A and one a allele. By random chance of which gametes are passed, about ¼ of their children should have two recessive alleles.
For your traits of tongue rolling, hitchhikers thumb, widows peak, and ear attachment, create a Punnett square for possible allele combinations that you and one other person in the class might pass to children if you mated. Use the Punnett square results to estimate the fraction of your children who would have each of the traits If you dont finish in class, finish for homework.
Sample pedigree to do as a class. Bent finger (dominant trait) Moms side of the familydads side Great Grandfatheryes Great Grandmother no Grandfathernoyes Grandmotheryesno Motherno Fatheryes Child no