11.1 basic patterns of human inheritance
DESCRIPTION
11.1 BASIC PATTERNS OF HUMAN INHERITANCE. WHAT YOU WILL LEARN -How to determine if an inherited trait is dom/rec -Examples of DOMINANT/RECESSIVE disorders -How a PEDIGREE shows a particular trait in families. MAIN IDEA. - PowerPoint PPT PresentationTRANSCRIPT
11.1 BASIC PATTERNS OF HUMAN INHERITANCE
WHAT YOU WILL LEARN-How to determine if an inherited trait is dom/rec-Examples of DOMINANT/RECESSIVE disorders-How a PEDIGREE shows a particular trait in families
MAIN IDEA
The inheritance of a trait is shown over several generations in a pedigree.
READING Q’s
REVIEW VOCAB: enzyme-PROTEIN that speeds up biological reactions
READING Q’s
IDENTIFY-CIRCLE the term that describes the genotype of a person who expresses a recessive trait
-homozygous: organism with 2 of the same alleles for a particlular trait
-DETERMINE the genotypes:recessive genetic disorderdominant genetic disorder
DD Dd dd
DD Dd dd
XX X
READING Q’s
EXPLAIN-Why do ganglioslides build up in the brain of people with Tay-Sachs disease?
-ENZYME missing that breaks down ganglioslides—fatty acids
READING Q’s
EXPLAIN-How scientist determine if achondroplasia developed from a new mutation
-achondroplasia is a dominant disorder: dwarfism-if BOTH parents are average height it dev from MUTATIONParents would be homozygous recessive so could only pass on a recessive allele—dominant allele would have to be a mutation
READING Q’s
EXPLAIN the purpose of a genetic pedigree-track a trait or disorder throughout several generations
DRAW the symbols used in a pedigree for:MALE= FEMALE=
READING Q’s
EVALUATE-Circle the carriers in the second generation
READING Q’s
CALCULATE-What percentage of the children in this family inherited Tay-Sachs disease?
-1/4=25%
READING Q’s
IDENTIFY-Do any grandchildren in this family have polydactyly?
-NO
READING Q’s
EXPLAIN-Why are recessive traits difficult to study?
-Not all people who carry the recessive allele have the trait-Don’t know if you are a carrier unless___
-1 parent shows the trait = homozygous recessive
-offspring shows trait = both parents carriers
GROUP WORK: APPLICATION NOTES
-As a group complete the guided note sheet using your knowledge from the reading.
REVIEW VOCAB
DEFINE: gene-segment of DNA on chromosomecarrier-heterozygous for a recessive disorder--Aa
RECESSIVE/DOMINANT GENETIC DISORDERS
COMPARE: RECESSIVE GENETIC DISORDERS
-only present if homozygous recessive-parents are carriers if don’t have disorder
DOMINANT GENETIC DISORDERS-present if have at least 1 dominant allele-must have a parent with the disorder
[mutations are exceptions]-don’t always appear until later in life
RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY: 1-four examples of recessive genetic disorders in humans1-CYSTIC FIBROSIS2-TAY-SACHS3-ALBINISM4-GALACTOSEMIA5-ALKOPTONURIA2-two examples of dominant genetic disorders in humans1-HUNTINGTON’S2-ACHONDROPLASIA
RECESSIVE/DOMINANT GENETIC DISORDERS
EXPLAIN why recessive disorders are more common than dominant disorders.-don’t always know there are carriers of disorder-parents may not know the disorder is in the family
RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY: the disease for each dominant/recessive disorders-caused by altered genes; results in lack of skin pigmentation
-ALBINISM-recessive
-characterized by body’s inability to tolerate galactose-GALATOSEMIA-recessive
-gene found on chromosome 15;characterized by lack of enzyme that breaks down fatty acids
-TAY SACHS-recessive
RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY: the disease for each dominant/recessive disorders-affects the nervous system; no treatment; breaks down part of brain
-HUNTINGTON’S-dominant
-affects mucus-producing glands, digestive enzymes, sweat glands
-CYCTIC FIBROSIS-recessive
-affects height and body size-ACHONDROPLASIA-dominant
RECESSIVE/DOMINANT GENETIC DISORDERS
-SHOW a cross between 2 carriers-what is the probability 2 carriers of cystic fibrosis will have a child w/CF?
F
FF
Ff
ff
Ff
f
F
f-25%
RECESSIVE/DOMINANT GENETIC DISORDERS
PREDICT: -can 2 normal height parents have a child w/achondroplasia?
a
aa aa
aa
aaa
a
a
RECESSIVE/DOMINANT GENETIC DISORDERS
PREDICT: -can 2 individuals w/achondroplasia have a child that is normal height?
A
AA Aa
aa
Aa
a
A
a
PEDIGREESSUMMARIZE: pedigree symbolsMALE
-square-FEMALE
-circle-AFFECTED MALE
-shaded square-AFFECTED FEMALE
-shaded circle-
CARRIER-half shaded symbol- / PARENTS--circle joined to square
PARENTS/OFFSPRING
-line down from parent/ circles/squares on second row-
PEDIGREE CHART
PEDIGREE CHART
GRANDPA X GRANDMA MOM X DAD GRAMPS X GRANNY
ANALYZING PEDIGREES
EVALUATE: the inheritance of achondroplasia shown in the pedigree
-parent w/ disorder-father
-#children with disorder-1 / 1st born son
-genotype of younger son-homozygous recessive / aa
ANALYZING PEDIGREESANALYZE and RESPOND: -RECALL if the trait is rec or dom based on the following information: -In the pedigree, individuals I-1 and I-2 are unaffected -- have affected childRECESSIVE DOMINANT-SPECIFIY if parents II-1 and II-2, who have an affected child, are carriers of that traitCARRIER NOT A CARRIER-TELL whether there is a dominant gene in the genotype of II-4NONE A LEAST ONE-Individual II-1is in generation 2 TRUE FALSE
X
X
X
X
ANALYZING PEDIGREES
THINK BACK and RESPOND: -A scientist uses a pedigree to study family historyTRUE FALSE-A pedigree traces the inheritance of a particular trait through only two generationsTRUE FALSE-In a pedigree, one who does not express the trait is represented by a darkened circle/squareTRUE FALSE-In a pedigree, a horizontal line between 2 symbols shows that these individuals are the parents of the offspringTRUE FALSE
X
X
X
X
MANY
ANALYZING PEDIGREES
DIAGRAM: Suppose both parents can roll their tongues but their son cannot.IDENTIFY this trait as: dominant recessiveDRAW a pedigree showing this trait LABEL each symbol with the appropriate genotype
What was the probability that they would have a non-tongue roller offspring? (hint: punnet square)
-both parents carry recessive gene-parent genotype Tt-son genotype tt
-probability of child tt= 25%
Connecting Pedigree Symbols
parents
offspring
EX- PEDIGREE CHART
Interpreting a Pedigree Chart1- Determine whether the trait/disorder is
dominant or recessive
-If the trait/disorder is dominant, one of the parents must have the disorder-If the trait/disorder is recessive, neither parent has to have the disorder because they can be heterozygous
• Dominant or Recessive?
PRACTICE: Interpreting
Answer
• Recessive
Dominant or Recessive?
PRACTICE: Interpreting
Answer
Dominant
Interpreting a Pedigree Chart
2- Determine if the pedigree chart shows an autosomal or X-linked trait/disorder
-If most of the males in the pedigree are affected the trait/disorder is X-linked -If it is a 50/50 ratio between men and women the trait/disorder is autosomal.
PRACTICE: Interpreting
Is it Autosomal or X-linked?
Answer
Autosomal
Summary
-Pedigrees are family trees that explain your genetic history.
-Pedigrees are used to find out the probability of a child having a trait/disorder in a particular family.
-To begin to interpret a pedigree-determine if the trait/disorder is:
1-dominant or recessive2-condition is autosomal or X-linked
PEDIGREE PRACTICE A
PEDIGREE PRACTICE B
PEDIGREE PRACTICE C
PEDIGREE PRACTICE D
INVESTIGATING HUMAN PEDIGREES
-USE the information provided in the transcript to construct a pedigree showing hairy earlobes* in a family *HE
-DETERMINE the oldest couple in the family-DRAW their pedigree symbols—include names-CONTINUE with other members in the family-DETERMINE genotypes as you gather enough information