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Human Heredity Sections 14-1 and 14-2

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Title: Human Heredity Sections 14-1 and 14-2


1
Human HereditySections 14-1 and 14-2
  • Objectives
  • 7.2 Interpreting inheritance patterns shown in
    graphs and charts
  • 8.5 Relating genetic disorders and disease to
    patterns of genetic inheritanceExamples
    hemophilia, sickle cell anemia, Down's syndrome,
    Tay-Sachs disease, cystic fibrosis, color
    blindness, phenylketonuria (PKU)

2
Human Chromosomes
  • How many chromosomes do we have?
  • Answer 46
  • How many of those are sex chromosomes?
  • Answer 2
  • What are the possible combinations of sex
    chromosomes?
  • Answer XX or XY
  • What are the other chromosomes called?
  • Answer autosomes

3
Karyotype
Source http//www.dnalc.org/view/16243-Gallery-8-
Human-female-karyotype.html
  • Def a picture of chromosomes, taken in mitosis
    metaphase, and paired up.
  • Why would the picture be taken at this point?

4
Pedigree Charts
Source http//www.citruscollege.edu/lc/archive/bi
ology/Pages/Chapter10-Rabitoy.aspx
5
Pedigree Charts Activities
  • Class Activity Figure 14-3, p.342
  • Individual Assignment Problem Solving, p.343.
    Add the following questions
  • Identify the genotype of each individual.
  • Is albinism a dominant or recessive trait?
  • What is the probability of the second-generation
    couple having another albino child?

6
Sex-Linked Genes
  • The X chromosome is much larger than the Y
    chromosome, carrying many more genes. (See Figure
    14-12, p.350)
  • More than 100 sex-linked genetic disorders have
    been mapped to the X chromosome.

7
Sex-Linked Genes
  • Since males have only one X chromosome, if an
    allele for a disorder is present on that
    chromosome, the trait will be expressed.
  • Common sex-linked disorders
  • Colorblindness
  • Color vision is controlled by three genes on the
    X chromosome.
  • 1 in 10 males in the U.S. have some form of
    colorblindness.
  • Hemophilia 2 genes on the X chromosome help
    control blood clotting (1/10,0000)
  • Duchenne Muscular Dystrophy (1/3000)

8
X-Chromosome Inactivation
  • Females have two X chromosomes.
  • One of those chromosomes is switched off,
    becoming a Barr body --- a dense (but inactive)
    region in the nucleus.
  • Males cannot switch off their X chromosome.

Source http//www.123rf.com/photo_2531003_spotted
-cat-with-no-tail-stands-attentive-and-alert.html
9
Chromosomal Disorders
  • Nondisjunction of homologous chromosomes during
    _____________, would give gametes abnormal
    numbers of chromosomes.
  • When these gametes become diploid again, the
    number of chromosomes is abnormal.
  • Some of these zygotes cannot survive others
    produce offspring with genetic disorders.

10
Chromosomal Nondisjunction
Source http//drugline.org/img/term/meiotic-nondi
sjunction-9351_3.JPG
11
Some Nondisjunction Disorders
  • Down syndrome
  • Autosomal nondisjunction
  • 3 copies of chromosome 21 (trisomy 21)

Source http//www.buzzle.com/articles/teaching-ch
ildren-with-down-syndrome.html
12
Some Nondisjunction Disorders
  • Sex chromosome disorders
  • Turners syndrome females with only one X
    chromosome
  • Fertile
  • Sex organs do not develop at puberty
  • Klinefelters syndrome males with too many X
    chromosomes
  • Interferes with meiosis, usually not permitting
    reproduction
  • No known cases of babies born without an X
    chromosome, so it must contain genes important
    for survival.

13
Some Nondisjunction Disorders
  • Sex chromosome disorders
  • Y chromosome contains a sex-determining region
    necessary to produce male sexual development
  • Can develop even in the presence of multiple X
    chromosomes
  • Will not develop if this region of the Y
    chromosome is absent.

14
DISORDER DETECTIVES ACTIVITY
  • http//www.youtube.com/watch?vth6Njr-qkq0
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