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Download Unit: Human Genetics - Each species has a specific number of
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Unit: Human Genetics Human Chromosomes - Each species has a specific number of chromosomes Humans = ___ - Where do we get them? _____________________________________ - What type of cell is involved in sexual reproduction? _____________ - Gametes have __________________ of chromosomes (___) Haploid (n) - They come together during fertilization to give us _____ chromosomes Diploid (2n) 23 + 23 = 46 - We have two types of chromosomes: 1. Autosomal chromosomes (aka ___________) - All chromosomes other than _______________ - 22 pairs 2. Sex chromosomes Sex Determination - What determines a baby’s sex? ________________ - Only _____ pair Could be X or Y Female = ______ Male = _____ - What sex chromosomes can men and women pass on? Women = only X Men = X or Y - Who determines the sex of the baby? Male or female? _________ - What are the chances a baby will be a boy? A girl? _________ - In humans 2 of the 46 chromosomes are sex chromosomes (XX or XY) - The other ____ chromosomes are called autosomes. Autosomes - Autosome = Opposite of sex chromosome Karyotypes - How do scientists study chromosomes? They use a _______________. - A karyotype is a picture of chromosomes grouped ____________________________________. How do they make a karyotype? - Cells are photographed during _____________. - The chromosomes are cut out of the picture and put in pairs - The pairs are in order from ____________________________________. Uses of karyotypes Disorder Human Heredity Pedigrees Uses of Pedigrees -What do scientists look for? – Are there 46 chromosomes? – Are there 2 identical pairs of each autosome and 2 sex chromosomes? – Are any chromosomes missing pieces or mixed up? Uses: - To detect __________________________. - For ____________________ prospective parents - Disorder = ______________________________ - What is heredity? ________________________________________ - A _________________________ is used to observe the inheritance of a given trait over generations in a family. - A pedigree shows ______________________________________. - Genetic counselors use pedigree charts to determine the _____________ of family members. Label: A circle= ____________ This shows the relationship of ______________ ______________ _______ __________ = expresses the trait. Polygenic Traits This represents a __________ A square = _________. ___________ = does not express the trait. - Not all human traits are controlled by a ______________________. Example: Aa - Some traits are polygenic (trait controlled by ____________________) Example: AaBbCc Environmental Factors Sex-linked Traits Sex-linked Traits in Males and Females - What else can affect traits? - Environmental factors For example, __________________________________________ Human traits can be: - __________________________________ or ___________________________________ - Some genes are only carried on the sex chromosomes = _______________________________. - More than 100 sex-linked genetic disorders have now been mapped to the ______________________________. - The Y chromosome is much ___________ than the X chromosome. - It appears to contain only a few genes. - Sex-linked traits are more likely to be passed on to males than females. Why? - Females have 2 X chromosomes Possible genotypes: XHXH normal XHXh XhXh ___________ __________ - Carrier carries the recessive gene but does not ___________________ (heterozygous) - Males have only ______ X chromosome - ___________________does not carry many genes - Possible genotypes: XHY Sex-linked Disorders XhY Normal ___________ - For a recessive allele to be expressed in females, they must have 2 copies: X __ X___ - Since males have just one X chromosome, ______ X-linked alleles are expressed even if they are recessive: X____Y___ Common sex-linked recessive traits: - Colorblindness = Cannot see _________________________ - ________________ = blood cannot clot due to lack of normal blood clotting protein Color-blindness - Found in about 1 in 10 males vs. 1 in 100 females Female genotypes: XCXc = Carrier XcXc = _____________ Males genotypes: XCY = ______________ XcY = Colorblind Sex-linked Problems Example 1: Colorblindness XCXc (carrier) Hemophilia x XCY (normal) Example 2: Hemophilia (Blood does not clot, so you bleed longer) H= ________________________________________ h= hemophilia Carrier mother & Hemophiliac Father XHXh XhY - Hemophiliacs can bleed to death from cuts and may suffer internal bleeding if bruised. Autosomal Traits - Result from genes carried on autosomes Affect males and females equally - Genetic disorders can be caused by a recessive, dominant, or codominant allele. Recessive alleles - Phenotype expressed only by ___________________ recessive (tt) - Heterozygote (Tt) acts as a ________________ Cystic fibrosis - Caused by a __________ of 3 DNA bases - Defective gene found on chromosome 7 - The protein made is not normal - Thick mucus produced that clogs lungs; digestive problems; get infections easily - Dominant alleles are expressed ______________________________ ____________________________________________ - If a disorder is caused by a dominant allele: - The protein produced by the abnormal gene inactivates the Dominant alleles normal protein or ____________________________________________ Huntington's Disease - Lose ability to walk, talk, and think (___________________________) - Caused by genetic mutation on chromosome 4 Codominant alleles - _________________________ are expressed Sickle Cell Disease - Just ______________________ is changed in a gene on chromosome 11 - Causes red blood cells to be sickle shaped rather than disc shaped - They get stuck in blood vessels & cause damage to tissues Sickle Cell Disease & Malaria Genetic and Chromosomal Disorders Mutations Types of Genetic Mutations - Individuals with both normal and sickle cell alleles are ___________ _________________________________________ - Malaria is a disease caused by a __________________ - In areas like Africa where malaria is present,________________ have an advantage - They survive and pass on the sickle cell allele - What causes these disorders? - _____________________: any change in the genetic material - can be caused by factors such as UV light, radiation, X-ray, chemicals Mutation can occur at two levels: 1) Genes 2) Chromosomes - DNA/ Gene Mutation involves changes in one or a few nucleotides 1) ______________________ - a change in single DNA base sequence Ex: Our big dog bit the man Our big dot bit the man 2) _______________________ - a base is “added” or “deleted” causing a “shift” of sequence Ex: Our big dog bit the man Our rbi gdo gbi tth ema n Oub igd ogb itt hem an Chromosome mutation - Involves changes in _________________________________________ Types of Chromosome Mutations Deletion = a piece is lost Duplication = a piece is duplicated Inversion = a piece is switched Translocation = a broken piece attaches to another chromosome Nondisjunction = ____________________________________________ Nondisjunction Meiosis I: Nondisjunction Extra chromosomes Turner Syndrome YO “Super Female” Klinefelter Syndrome Down Syndrome Missing chromosomes - One too few chromosomes (__________) - Sterile (cannot have children), shorter than average, heart defects, premature aging, shorter lives YO = _______________ - No babies have been reported being born without an X chromosome - ______________________= only one chromosome (XO) - ____________= one too many chromosomes (XXX, XXY, trisomy 21) - ________ Condition - Tall, small head, increased strength, possible retardation, infertile - ____________ condition - Most from non-disjunction in ______________ - Tall, some mental slowness - Poor male sex organ development; breast development; usually sterile - Trisomy _______ - 3 copies of chromosome 21 - Mild to severe mental retardation - Many lead productive lives