Genetics Exam 2 2
Terms
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copy deck
- Aneuploidy
- gain or loss of one or more chromosomes form normal (2n) diploid set
- Nullisomy
- (2n-2) always lethal and so unkown among live births, because both copies of a particular chromosome types are lost, so all genes on that particular chromosome are completely absent
- Monosomy
- (2n-1)usually lehtal in animals unless chromosome involved is a: 1)very small autosome 2)sex chromosome [XO, but YO lethal]
- Tetrasomy
- (2n+2) usually lethal in animals unless chromosome involved is a sex chromosome (such as XXXX or XXXY)
- Trisomy
- (2n+1) usually lethal in animals unless chromosome involved is a: 1)sex chromosome 2)very small autosome
- Down Syndrome
- [trisomy 21 John L. Down] origin of third copy of chromo#21, non-disjunction of this chromosome type during meiosis in either male or female parents (usually female)
- Results of Down Syndrome
- reduction of IQ, general health and life expectancy. Poor motor control, cheerful personality, broad flat face, fold corner of eyes
- Monosomy 21
- [presence of only 1 copy of this chromosome type] is non-existnet even though the diagrams of primary and secondary non-disjunction show that meiotic non-disjunction always produces equal numbers of n+1 and n-1 gametes [maternal age effect= higher age: higher chance]
- Origin of Aneuploidy
- chromosomal nondisjunction (meiotic accidents: failure of chromosmoes to seperate normally)
- Polyploidy
- more than 2 multiples of haploid (n) chromosome set present
- a)Polyploidy in animals and plants
-
rare in animals, common in plants (and important for agriculture)
diploid-2n
triploid-3n(sterile)
tetraploid-4n
pentaploid-5n(sterile)
hexaploid-6n - b)Polylpoidy origin of extra sets
-
1)autopolyploid
2)allopolyploidy -
1)Autopolyploid
2)Allopolyploidy -
1)ALL SETS FROM SAME SPECIES double fertilization [polyspermy] producing triploid offspring
2)MULTIPULE SETS FROM AT LEAST 2 SPECIES interspecific hybrization, as in commercial bread wheat, which is an allohexaploid (AABBDD) - Variation in Chromosome structure
-
a)Defective chromosome
b)Chromosome heterozygote
c)Balanced and Unbalanced
d)Chromosomes defects arise - Chromosome Heterozygote
- is defined to be one normal and one defective
- Defective Chromosomes
- are heritable-often passed unchanged to offspring
-
a)Balanced Chromosomal Mutation
b)Unbalanced Chromosmal Mutation -
a)no genetic information has been lost but location of certain genes has been altered
b)there is a gain or loss of genetic information compared to the normal situation - Chromosome Defects
- arise as a spontaneous double-stranded break or a pair of breaks (broken ends are 'sticky' but don't always re-join properly
- Potential Consequences of a break
-
a)loss of terminal piece(very bad)-unbalanced
b)abnormal reattachment(bad)-balanced
c)normal reattachment of broken pieces (best)-balanced - Terminal Deletion
-
(normal) ABCDEFoGHI and QRSTUoVWXYZ
(alter) BCDEFoGHI and QRSTUoVWXYZ - Intercalary Deletion
-
(normal) ABCDEFoGHI and QRSTUoVWXYZ
(alter) ABDEFoGHI and QRSTUoVWXYZ - Tandem Direct Duplication
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)ABABCDEFoGHI and QRSTUoVWXYZ - Tandem Inverted Duplication
-
(normal) ABCDEFoGHI and QRSTUoVWXYZ
(alter) ABBACDEFoGHI and QRSTUoVWXYZ - Tandem Indirect Duplication
-
(normal)ABCDEFoGHIand QRSTUoVWXYZ
(altered)ABBACDEFoGHI and QRSTUoVWXYZ - Dispersed Direct Duplication
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)ABCDEFoGABHI and QRSTUoVWXYZ - Dispersed Indirect Duplication
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)ABCDEFoGBAHI and QRSTUoVWXYZ - Paracentric Inversion
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)AEDCBFoGHI and QRSTUoVWXYZ - Pericentric Inversion
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)ABHGoFEDCI and QRSTUoVWXYZ - Reciprocal Translocation
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)QRSTCDEFoGHI and ABUoVWYZ - Non-reciprocal Traslocation
-
(normal)ABCDEFoGHI and QRSTUoVWXYZ
(altered)QRABCDEFoGHI and STUoVWYZ or ABCDEFoGHI and STUoVWXYZQR - (SPECIAL) pericentric inversion AND paracentric inversion
-
a)change chromosome shape [para=parallel]
b)don't involve the centromere, will leave a submetacetric chromosome as submetacentric [peri=around] - (classically) gene
-
1)unit of heredity controls a particular trait
2)unit of transmission b/w generations
3)unit of pheno expression w/in an individual - Particulate
- transmission b/w generations doesn't chnage the nature of the gene (EXCEPT GENE MUTATIONS)
- (Molecular) gene
- made of DNA but NOT ALL DNA is part of a gene [98% of human genome doesn't code for RNA transcript]
- Non-coded DNA
- 1)structure element of chromosome [centromere and telomeres]
- EUKARYOTES chromosomes- special protiens
- histones [structural elements without carrying genetic information]
- DNA
- breaks into monomers-- breaks into--nucleotides--breaks into--deoxyribose (5 carbon sugar), phosphate (PO4) and nitrogenous base: C T A G
- RNA
- breaks into monomers-- breaks into--nucleotides--breaks into--ribose (5 carbon sugar), phosphate (PO4) and nitrogenous base: C U A G
- Construction of gene mapping
- small pieces to overall big piece [cuts down on chance of undetected double crosses]
- Non-coding DNA
- can't be called alleles because they do segregate during meiosis DON'T produce pheno differences
- 1 map unit or 1% recombination
- approx equal to 1,000,000 bp of DNA
- haploid gneome contains
- 3 Gb of DNA
- diploid genome contains
- 6 Gb of DNA
- 4 secrets of DNA sucess
-
d)Expression of genetic info
[most genes control production of particular proteins through mRNA intermediate but some genes make tRNA or rRNA rather than mRNA - 3 stop codons
-
UAA, UGA or UAG
[always written 5'-nnn-3'] - n
- any nucleotide (A,C,U,G)
- y
- either pyrimidine (C,U)
- r
- either purine (A,G)
- Overview of genetic code (9)
- 9)genetic code is universal SINGLE CODING DICTIONARY used by most a)prokaryotic b)eukaryotic
- Consequences of synonymy (redundancy) of genetic code (2)
-
1)many third position base subsitutions (mutations) don't alter the amino acid sequence
2)cell doesn't need 61 different tRNAs, each serving a different mRNA codon - Synonymous (silent) substitution
- a mutation in the DNA that results in an altered mRNA swquence but NO CHANGE in the polypeptide sequence
-
mRNA
tRNA
rRNA -
=messenger RNA
=transfer RNA
=reibosomal RNA -
mRNA gene
tRNA gene
rRNA gene -
=gene coding for messenger RNA
=gene coding for transfer RNA
=gene coding for ribosmal RNA -
ssDNA
ssRNA
dsRNA -
=single strand DNA
=single strand RNA
=double strand DNA - Information flow (focus on protien-coding genes)
-
dsDNA-(transc)-ss mRNA-(transl)-polypeptide
dsDNA-(transc)-ss rRNA (never translated)
dsDNA-(transc)-ss tRNA (never tranlated) - Nucleic acids (DNA or RNA)
- long molecules(polymers) made of building blocks(nucleotides) that are themselves composed of three subunits
- Nitrogen Bases: Pyrimdines
- Cytosine, Uracil and Thymine (single ring)
- Nitrogen Bases: Purines
- Adenine and Guanine (double ring)
- Sugar: Ribose (RNA)
- 5 carbon sugar (has OH attached to 2,3 carbons)
- Sugar: (Deoxyribose)
- 5 carbon sugar (has OH attached 3 and H attached 2 carbon)
- Nucleotide (3)
- nitrogenous base + sugar + phosphate group--(2 neg charges)
- Watson-Crick double helix model of DNA (source)
- Chargaff's rules, X-ray diffraction data (relative numbers= molar amounts of each base present in DNA from various species)
- Chargaff's Rule
-
[A]=[T] or [A]/[T]=1
[C]=[G] or [C]/[G]=1
[A+G]=[C+T] or [purines]=[pyrimdines]
[A]=[T]=[C]=[G]=1/4 - Other possible ratios, like %GC
-
%GC = {[G + C]/[G + C + A + T]} X 100
(OR ASYMMETRY RATIO)
[A + T]/[C + G] - X-ray diffraction data
-
suggesting that the DNA molecule is:
a)helical
b)long and narrow
c)has a repeating structure
d)is composed of >1 polynucleotide chain - Details about DNA
-
a)two chains have anti-parallel orientation
b)pairs of bases project from opposite sugar-phosphate strands meet in center of molecule (HYDROGEN BONDS] - Two types of basepairs (bp) can form
-
a) A=T (LESS DENSE)
b) C=G (MORE DENSE/SMALLER/ THERMOSTABILITY) - Number of (bp) for every 360 degree twist of the molecule
- 10 bp distance
- DNA molecule
- right-handed nature of DNA/ alternating major and minor grooves run along the right- hand fashion
- DNA Grooves
- sites for DNA-binding proteins
- Width of double helix
- 2 nm (including phosphate backbone)
- Hydrogen bonds and hydrophobicity
- stability of genetic material (dissolve in water due to the neg charge of the phosphate groups on the outside of the molecule, whater cannot cause the two strands to seperate [NEED TO COLD, DRYNESS, HIGHT SALT]
- Conservative DNA replication
- new strands
- Semi-conservative DNA replication
- parental acts as a template with a new strand
- Dispersive DNA replication
- segmented replication in new strands