Bell Ringer: Copy the following words to define for homework. 1) Carrier 2) Pedigree 3) Autosome 4) Codominance 5) Incomplete Dominance 6) Multiple Alleles 7) Sex Chromosome 8) Sex-Linked Trait 9) Karyotype 10)Nondisjunction 11)Telomere 12)Deletion 13)Inversion 14)Translocation 15)Down Syndrome 16)Turner’s Syndrome 17)Klinefelter’s Syndrome
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Bell Ringer: Copy the following words to define for homework. 1)Carrier 2)Pedigree 3)Autosome 4)Codominance 5)Incomplete Dominance 6)Multiple Alleles 7)Sex.
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Bell Ringer: Copy the following words to define for homework.
1) Carrier
2) Pedigree
3) Autosome
4) Codominance
5) Incomplete Dominance
6) Multiple Alleles
7) Sex Chromosome
8) Sex-Linked Trait
9) Karyotype
10)Nondisjunction
11)Telomere
12)Deletion
13) Inversion
14)Translocation
15)Down Syndrome
16)Turner’s Syndrome
17)Klinefelter’s Syndrome
Benchmark Test Info
• Point Breakdown
• 52 pts Participation
• 48 pts (2pts each) for the 24 questions we’ve already covered.
• TALKING/LOOKING AROUND will result in the loss of your 52 participation points.
Bell-Ringer
• Grab a packet of guided notes from the
back table.
Complex Inheritanceand Human Heredity 11
The Big Idea
Human inheritance does not always follow
Mendel’s laws.
Main Idea #1The inheritance of a trait over several
generations can be shown in a pedigree.
Recessive Genetic Disorders
• Remember - recessive traits can be masked by a dominant trait.
• Therefore, a person who is heterozygous for a characteristic may be considered a carrier for that trait since it will not be expressed.
• Even though a carrier is not affected by the trait, they can pass the trait on to future generations.
• In order for the recessive trait to show in the individual, the person must be homozygous recessive.
Common Recessive Disorders
• Cystic Fibrosis
• Affects the mucus-producing glands, digestive enzymes, and sweat glands
• Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat
• Without sufficient chloride ions in the cells, a thick mucus is secreted
• The mucus clogs ducts in the pancreas, causes problems with digestion, and blocks some of the tiny passages in the respiratory system.
Common Recessive Disorders
• Albinism
• Caused by altered genes, resulting in the absence of melanin (color pigment) in the hair and eyes
• Common characteristics include: white hair, very pale skin, and pink pupils
• Tay-Sachs Disease
• Caused by the absence of an enzyme responsible for breaking down fatty acids
• The fats begin accumulating in the brain, destroying brain cells and mental deterioration.
Dominant Genetic Disorders• Some genetic disorders are controlled by a dominant
allele.
• People who have only one copy of this allele will display the trait. Only those who are homozygous recessive will not have the disorder.
• Huntington’s Disease
• Disease that gradually destroys the nervous system. Symptoms usually begin between the ages of 30 and 50.
• Achondroplasia
• Genetic condition that causes small body size and limbs that are comparatively short. This is the most common form of dwarfism.
Pedigrees• A pedigree is a diagram that traces the inheritance
of a particular trait through several generations.
• Males are represented by squares, and females by circles.
• One who is affected by the trait will have a symbol that is colored in, while those that are unaffected by the trait will have an unfilled symbol.
Pedigree
Let’s Practice!!!Make this correction:
• Second question for #3 should read, What are the sexes of the
children?
Main Idea #3Chromosomes can be studied using
karyotypes.
Karyotypes
• A karyotype is a picture of a person’s chromosomes.
• Chromosomes are taken from the stage of metaphase and stained.
• They are then placed in order of decreasing size. The last pair is the sex chromosome pair.
• Disorders caused by an incorrect number of chromosomes or malformed chromosomes are the easiest to identify using a karyotype.
Normal Karyotypes
Telomeres
• Telomere caps consist of DNA associated with proteins.
Nondisjunction
• Homologous chromosomes separate during the final steps of meiosis to ensure that each developing sperm or egg receives one copy of each chromosome.
• Nondisjunction is the failure of a pair of homologous chromosomes to separate properly.
• Resulting sex cells will either have an extra chromosome (trisomy) or a missing chromosome (monosomy).
Down Syndrome
• One of the most common disorders due to nondisjunction is Down syndrome, also known as trisomy 21.
• Down syndrome occurs when the person has a third copy of the 21st chromosome.
• Common features include: short stature, heart defects, distinctive facial features, and mental disability.
Disorders Due to Nondisjunction of Sex Chromosomes
Klinefelter Syndrome
(XXY)
Jacob’s Syndrome
(XYY)
Turner’s Syndrome
(XO)
Trisomy X Syndrome
(XXX)
Types of Mutations• Mutations can involve an entire chromosome or a
single DNA nucleotide, and they may take place in any cell.
• Germ-cell mutations occur in an organism’s gametes (germ cells).
• These do not affect that organism, but may be passed on to their offspring the germ cell becomes fertilized.
• Somatic mutations occur in an organism’s body cells and can affect the organism.
• These mutations cannot be passed on to offspring.
• Some examples include skin cancer and leukemia.
• Lethal mutations cause death, usually before birth.
Chromosome Mutations
• Deletion (1)- results in the loss of a piece of chromosome due to the breakage of that chromosome; genetic information will be lost
• Duplication (2)- results in the copying of a segment of the chromosome
• Inversion (3)- a segment of a chromosome breaks off and reattaches itself to the chromosome in a reversed order
Chromosome Mutations
• Insertion (1) - a segment of a chromosome breaks off and reattaches itself to another homologous chromosome
• Translocation (2) - segments of chromosomes break off and exchange places on different chromosomes
Chromosome Mutations
• Nondisjunction is also a type of chromosome mutation. It affects the total number of chromosomes instead of pieces of individual chromosomes.