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Let’s think about it…. W hat are autosomes? What are sex chromosomes? What are the human autosomes and sex chromosomes? What are the chances of two parents conceiving a boy? A girl?. Ch 12 Inheritance patterns and Human Genetics . Human chromosome review. 23 pairs 1-22 = autosomes

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Let s think about it
Let’s think about it…

  • What are autosomes?

  • What are sex chromosomes?

  • What are the human autosomes and sex chromosomes?

  • What are the chances of two parents conceiving a boy? A girl?


Ch 12 inheritance patterns and human genetics

Ch 12 Inheritance patterns and Human Genetics


Human chromosome review
Human chromosome review

  • 23 pairs

  • 1-22 = autosomes

  • 23rd pair = sex chromosome

    • What are they two sex chromosomes?

  • Female: XX

  • Male: XY

    • Y chromosome contains SRY gene

  • SRY: Sex determining Region Y- gene coding for production of male gonads (testes)


Sex linked genes and traits
Sex-linked genes and traits

  • Sex-linked traits: trait coded for by alleles on a sex chromosome

  • X chromosome much larger = many more gene than Y

  • Examples:

    • SRY (Y-linked)

    • Color blindness (X-linked)

    • Hemophilia (x-linked)


Linked genes
Linked genes

  • Linked genes: pairs of genes that tend to be inherited together

  • Genes close to each other on chromosome

  • Example

    • If crossing over occurs, A & B are likely to be inherited together

    • A & E less likely


Mutations
Mutations

  • Change in nucleotide base sequence

  • Germ cell mutation: in gametes

    • does not affect organism

    • can be passed down to offspring

  • Somatic cell mutation: in body cells

    • Can affect organism

  • Lethal mutations: can cause death (usually before birth)


Mutations1
Mutations

  • Chromosomes can be:

    • Deleted

    • Flipped around (inverted)

    • Moved to the wrong chromosome

  • DNA bases (& sequences) can be:

    • Deleted

    • Inserted

    • Substituted

    • Etc.


Mutations2
Mutations

  • Two main categories:

  • Chromosomal (affect chromosome)

    • Nondisjunction: chromosomes fail to separate during meiosis

      • Down Syndrome


2. Gene (affect DNA sequence)

  • Frameshift: affects one codon and as a result, all codons downstream are changed (shifts the reading frame

  • ATC/GTA/GCT/GCT/ATT

  • ATC/GTT/AGC/TGC/TAT/T


  • Chromosomal
    Chromosomal

    • Nondisjunction video



    12 2 human genetics
    12-2 Human genetics

    • Pedigree: diagram that shows how a trait is inherited over several generations


    Pedigrees used to
    Pedigrees used to:

    • See patterns of inheritance

    • See if trait is autosomal or sex-linked

    • Dominant or recessive


    Genetic disorders and diseases
    Genetic Disorders and Diseases

    • http://www.youtube.com/watch?v=8s4he3wLgkM


    Genetic traits and disorders
    Genetic traits and disorders

    • Some traits have a single gene with two or more alleles

      • Blood type

      • Cystic fibrosis

    • Most human traits are polygenic: characters influenced by several genes

    • Skin color; 3-6 genes


    Genetic traits and disorders1
    Genetic traits and disorders

    • Complex characters: influenced by environment and genes

      • Skin color exposed to sunlight

      • Height

      • Breast cancer

      • Diabetes

      • Heart disease


    Multiple alleles
    Multiple alleles

    • Genes have more than three alleles

    • ABO blood type


    Incomplete dominance
    Incomplete dominance

    • Heterozygote is an intermediate phenotype


    X linked traits
    X-linked traits

    • More common in males (x-linked recessive)

    • Males inherit X from mom and no other

    • No possibility of heterozygous

    • Colorblindness

    • http://www.youtube.com/watch?v=8Aaivktz8G0


    Single allele traits
    Single allele traits

    • Single allele of a gene controls these traits

    • <200 human traits

    • Huntington’s Disease

    • Autosomal dominant

    • Symptoms @30-40 y. o.


    Detecting genetic disease
    Detecting genetic disease

    • Genetic screening: examination of a person’s genetic information

    • Need DNA from embryo

    • Amniocentesis: removal of amniotic fluid surrounding fetus

      • 14th-15th week

    • Chorionic villi sampling: sample of chorion villi (tissue surrounding developing embry)

      • 8th-10th week


    Open text to page 246
    Open text to page 246

    • Copy table in your notes

    • You only need the disorder, pattern of inheritance, and brief description of symptoms


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