3201_obj_genetics_modern_ideas.doc | |
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Section 2 – Genetics: Modern Ideas
Chapter 16 – section 16.3 on-wards, beginning p. 545
Objective 1
Mendel
•each trait had two factors
•factors segregate so each gamete has one factor
Sutton and Boveri
•studied phases of meiosis
•behaviour of chromosomes same as behaviour of ‘factors’ (pic P. 546)
•3 observations
–chromosomes occur in pairs
–pairs segregate during meiosis
–chromosomes align independently of each other
•each gamete gets one chromosome (chromatid) from each pair
•has no impact on the presence or absence of the other chromosomes
Objective 2
Chromosome theory of inheritance - theory of inheritance that states that genes are located on chromosomes, and the separation and independent assortment of these chromosomes accounts for inheritance patterns
Objective 3
Thomas Morgan (1910)
•studied fruit flies
•crossed two red eyed parents and discovered white-eyed offspring
•nothing too strange about that
•crossed red-eyed female offspring of a white-eyed male with normal red-eyed male,
•all females had red eyes
•half males had red, half had white
•eye color may be linked to sex
•eye color located on X-chromosome
Objective 3&6
•also discovered that some traits weren’t inherited independently
•inherited together - genes located on same chromosome, didn’t segregate
•linked genes
•sometimes though, linked genes do separate
•whether they separate depends how close together they are on the chromosome
Objective 4
•Gene linkage - genes located on the same chromosome that usually don’t segregate, and are therefore inherited together (blond hair and blue eyes found on same chromosome)
•crossing over - in cellular reproduction, the process in which non-sister chromatids exchange genes during prophase I of meiosis allowing for the recombination of genes.
Objective 5 & 6
•gene-chromosome theory - theory that states that genes exist at specific sites arranged in a linear fashion along chromosomes. Accounts for why some genes found on the same chromosomes do segregate in crossing over.
•genes located close together will almost always be inherited together
genes located at opposite ends of a chromosome are more likely to be separated during crossing over
Objective 7
•Mendel’s law of independent assortment RESTATED: if crossing over does not occur, genes located on different chromosomes will assort independently and genes located on the same chromosome will be inherited together.
Objective 8
Sex- Linked Inheritance
•passing of some traits depends on sex of the parent
•these genes are located on sex chromosomes
•sex-linked inheritance - the transfer of genes on the X or Y chromosome from one generation to the next
•gene located on Y chromosome only - Y-linked
•We will focus on X-linked
•very few Y-linked traits are known (smaller chromosome)
•ex. Eye color on fruit flies carried on X
•white - recessive
Objective 9
sex linked defects more common in males than females
Woman Man
XC XC - normal XCY - normal
XC Xc - normal XcY - colorblind
Xc Xc - colorblind
Objective 10 (see file below)
Objective 11
polygenic traits -pattern of inheritance in which a trait is controlled by more than one gene
Objective 12 - See file below
Objective 13
karyotypes - illustration or photograph of the chromosomes in the nucleus of a somatic cell in an organism
Chapter 16 – section 16.3 on-wards, beginning p. 545
Objective 1
Mendel
•each trait had two factors
•factors segregate so each gamete has one factor
Sutton and Boveri
•studied phases of meiosis
•behaviour of chromosomes same as behaviour of ‘factors’ (pic P. 546)
•3 observations
–chromosomes occur in pairs
–pairs segregate during meiosis
–chromosomes align independently of each other
•each gamete gets one chromosome (chromatid) from each pair
•has no impact on the presence or absence of the other chromosomes
Objective 2
Chromosome theory of inheritance - theory of inheritance that states that genes are located on chromosomes, and the separation and independent assortment of these chromosomes accounts for inheritance patterns
Objective 3
Thomas Morgan (1910)
•studied fruit flies
•crossed two red eyed parents and discovered white-eyed offspring
•nothing too strange about that
•crossed red-eyed female offspring of a white-eyed male with normal red-eyed male,
•all females had red eyes
•half males had red, half had white
•eye color may be linked to sex
•eye color located on X-chromosome
Objective 3&6
•also discovered that some traits weren’t inherited independently
•inherited together - genes located on same chromosome, didn’t segregate
•linked genes
•sometimes though, linked genes do separate
•whether they separate depends how close together they are on the chromosome
Objective 4
•Gene linkage - genes located on the same chromosome that usually don’t segregate, and are therefore inherited together (blond hair and blue eyes found on same chromosome)
•crossing over - in cellular reproduction, the process in which non-sister chromatids exchange genes during prophase I of meiosis allowing for the recombination of genes.
Objective 5 & 6
•gene-chromosome theory - theory that states that genes exist at specific sites arranged in a linear fashion along chromosomes. Accounts for why some genes found on the same chromosomes do segregate in crossing over.
•genes located close together will almost always be inherited together
genes located at opposite ends of a chromosome are more likely to be separated during crossing over
Objective 7
•Mendel’s law of independent assortment RESTATED: if crossing over does not occur, genes located on different chromosomes will assort independently and genes located on the same chromosome will be inherited together.
Objective 8
Sex- Linked Inheritance
•passing of some traits depends on sex of the parent
•these genes are located on sex chromosomes
•sex-linked inheritance - the transfer of genes on the X or Y chromosome from one generation to the next
•gene located on Y chromosome only - Y-linked
•We will focus on X-linked
•very few Y-linked traits are known (smaller chromosome)
•ex. Eye color on fruit flies carried on X
•white - recessive
Objective 9
sex linked defects more common in males than females
- many
genetic disorders are recessive conditions
- carried
on X chromosome
- for
a woman to be colorblind, her father must be, and her mother must be a carrier
- a
man only needs to inherit one copy of the recessive allele from his mother (he
can be colorblind even if she=s normal (XC Xc)
Woman Man
XC XC - normal XCY - normal
XC Xc - normal XcY - colorblind
Xc Xc - colorblind
Objective 10 (see file below)
Objective 11
polygenic traits -pattern of inheritance in which a trait is controlled by more than one gene
- many
traits working together B range of variations
- ex.
Ears of corn (page 550)
- longest
ear length AABB
- shortest
ear length aabb
- least
common (only one combination possible to get this phenotype)
- medium
is most common
- longest
B AABB (all four dominant)
- long B AaBB or AABb (3 dominant)
- medium
B any two dominant (AAbb, AaBb, AaBb,
etc)
- short
B one dominant (Aabb, aaBb, etc)
- shortest
B 0 dominant (aabb)
Objective 12 - See file below
Objective 13
karyotypes - illustration or photograph of the chromosomes in the nucleus of a somatic cell in an organism
- cells
are grown in a glass container
- solution
added to stop cell division at metaphase
- chromosomes
are separated from the cells, stained and photographed
- arranged
in pairs according to shape, size and appearance
- used
to detect disorders (extra or less chromosomes, translocations, etc
sex_linked_punnett_square_problems.docx | |
File Size: | 12 kb |
File Type: | docx |
in_class_assignment__sex_linked_traits.docx | |
File Size: | 12 kb |
File Type: | docx |