Unit 3 review
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Unit 3 Review. This version is for posting to the class web site. Genes are located on chromosomes and are the basic unit of heredity that is passed on from parent to child, through generations.

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Unit 3 Review

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Unit 3 review

Unit 3 Review

This version is for posting to the class web site.


Unit 3 review

Genes are located on chromosomes and are the basic unit of heredity that is passed on from parent to child, through generations.

  • Explain how a chromosome mutation could occur and why mutations are detrimental to the organism in which they take place.

  • Explain why human males may suffer from having just one copy of the X chromosome, while females have two.


Unit 3 review

O

O

O

O–

O–

O–

P

P

P

O

O

O

O

O

O

5 end

O

OH

3 end

Hydrogen bond

P

Remember:

phive-phosphate

What do 3 and 5 stand for???

What does antiparallel mean?

–O

O

OH

H2C

O

A

T

O

CH2

O

O

P

O

–O

O–

O

P

O

H2C

O

O

G

C

O

O

CH2

O

P

–O

O

H2C

O

C

G

O

O

CH2

O

P

–O

O

H2C

O

A

T

O

CH2

OH

3 end

Figure 16.7b

5 end

(b) Partial chemical structure


Punnett squares

Punnett Squares

  • Punnett squares help us visualize segregation of allelles:

All F1’s show dominant trait

3:1 F2 ratio on eye color trait indicates heterozygous cross.


Operons are karyotic

lac operon

DNA

lacl

lacz

lacY

lacA

RNApolymerase

3

mRNA 5

mRNA 5'

mRNA

5

-Galactosidase

Permease

Transacetylase

Protein

Inactiverepressor

Allolactose(inducer)

(b)

Lactose present, repressor inactive, operon on. Allolactose, an isomer of lactose, derepresses the operon by inactivating the repressor. In this way, the enzymes for lactose utilization are induced.

Operons are ___karyotic


Unit 3 review

Why can’t this dad give hemophilia to his sons?

How could a girl end up with hemophilia?


Crossing over

Nonsister

chromatids

Prophase I

of meiosis

Tetrad

Chiasma,

site of

crossing

over

Metaphase I

Metaphase II

Daughter

cells

Recombinant

chromosomes

Figure 13.11

Crossing Over

  • Crossing over:

    • when does this happen?

    • the closer two alleles are on a chromosome, the ____ chance of being separated by crossing over.


Unit 3 review

How can you show that this pedigree is of an autosomal recessive trait?

What’s the diff between autosomal & sex-linked?


Multiple alleles

Multiple Alleles

  • Most genes exist in more than two allelic forms

    • Ex: ABO blood groups

    • Which type of blood cell(s)would be rejectedby a person withtype B blood?


Unit 3 review

mom

dad

What is Dad if 50% of offspring come out type A, and 50% come out type B?


Unit 3 review

If Y is a lethal allele, and it’s dominant, who will survive here?

Can you think of an example of a lethal dominant that does persist in the populationbecause it doesn’t kill tillmiddle age?


Unit 3 review

Sporophytes produce __ploid ______s by ___osis.

Gametophyes produce __ploid _______s by ___osis.


Unit 3 review

Key

Maternal set of

chromosomes

Possibility 1

Possibility 2

Paternal set of

chromosomes

Metaphase II

Daughter

cells

Combination 1

Combination 2

Combination 3

Combination 4

  • What is Independent assortment?

    • pairs of maternal and paternal homologues sort into gametes independently of the other pairs

Two equally probable

arrangements of

chromosomes at

metaphase I

Figure 13.10


W waxy w dull g green g yellow

W=waxy, w=dull; G=green, g=yellow

  • You can do a dihybrid Punnett for this problem, (WwGg x WwGg) or…

    • find probability of each character separately (dull and green)

    • then, multiply probabilities of dulland greentogether.

    • dull Green = wwGG or wwGg

x

= ¼ x ¾ =3/163/16 x 144 = 27


Unit 3 review

How are these virusus the same?

How are they different?


Unit 3 review

Same in all eukaryotes, from yeast to you. KNOW IT!


Unit 3 review

What are restriction enzymes?

What are they used for?


Movement of transposons and retrotransposons

New copy of

transposon

Transposon

DNA of genome

Transposon

is copied

Insertion

Mobile transposon

(a) Transposon movement (“copy-and-paste” mechanism)

New copy of

retrotransposon

Retrotransposon

DNA of genome

RNA

Reverse

transcriptase

Insertion

(b) Retrotransposon movement

Movement of Transposons and Retrotransposons

  • Eukaryotic transposable elements are of two types

    • Transposons, which move within a genome by means of a DNA intermediate

    • Retrotransposons, which move by means of an RNA intermediate

Figure 19.16a, b


Dna methylation

DNA Methylation

  • methylation of cytosines on the DNA strand lead to tight packing & reduces transcription

  • methylation patterns are copied during mitosis

  • what do we call it if methylation is passed to the next generation?


Unit 3 review

KNOW IT!

Figure 17.26


Unit 3 review

Acetylated histones

Unacetylated histones

(b) Acetylation of histone tails promotes loose chromatin structure that permits transcription

Figure 19.4 b

  • Histone acetylation …

    • loosens chromatin structure and enhance transcription


Lytic lysogenic phage infections

Lytic & Lysogenic phage infections:


The telemere problem in dna replication

5

Leading strand

Lagging strand

End of parental

DNA strands

3

Last fragment

Previous fragment

Lagging strand

RNA primer

5

3

Removal of primers and

replacement with DNA

where a 3 end is available

5

3

Second round

of replication

5

New leading strand

3

New lagging strand 5

3

Further rounds

of replication

Figure 16.18

Shorter and shorter

daughter molecules

The Telemere problem in DNA Replication

  • The ends of eukaryotic chromosomes get shorter with each round of replication

Primer removed but

cannot be replaced

with DNA because

no 3 end available

for DNA polymerase

Telemerase can restore these ends


Unit 3 review

3

2

1

3

5

Target

sequence

3

Genomic DNA

5

3

5

Denaturation:

Heat briefly

to separate DNA strands

5

3

Annealing: Cool to allow primers to hydrogen-bond.

Cycle 1

yields

2

molecules

Primers

Extension:

DNA polymerase

adds nucleotidesto the 3 end of each primer

Newnucleo-tides

Cycle 2

yields

4

molecules

Cycle 3

yields 8

molecules;

2 molecules

(in white boxes)

match target

sequence

DNA Amplification:

  • PCR procedure:

    • use specific primers to bind to each end of the segment you want.

    • use a heat resistant DNA polymerase

    • after about 20 cycles, target DNA (white boxes) greatly outnumber longer strands.


Unit 3 review

DdeI

DdeI

DdeI

DdeI

Normal  -globin allele

201 bp

Large fragment

175 bp

Sickle-cell mutant -globin allele

Large fragment

376 bp

DdeI

DdeI

DdeI

(a)

DdeIrestriction sites in normal and sickle-cell alleles of

-globin gene.

Sickle-cellallele

Normalallele

Largefragment

376 bp

201 bp175 bp

(b)

Electrophoresis of restriction fragments from normal and sickle-cell alleles.

Figure 20.9a, b

  • Restriction fragment analysis

    • Is useful for comparing two different DNA molecules, such as two alleles for a gene


How many cuts to get 9 pieces

How many cuts to get 9 pieces?


Unit 3 review

Why would we want to “steal” a gene and put it in a bacterial plasmid?

How could you do it?


Rna polymerase binding and initiation of transcription

Eukaryotic promoters

1

Additional transcription

factors

3

RNA Polymerase Binding and Initiation of Transcription

  • Promoters signal the initiation of RNA synthesis

  • Transcription factors

    • Help eukaryotic RNA polymerase bind to promoter sequences

TRANSCRIPTION

DNA

Pre-mRNA

RNA PROCESSING

mRNA

Ribosome

TRANSLATION

Polypeptide

Promoter

5

3

A

T

A

T

A

A

A

A

T

A

T

T

T

T

3

5

TATA box

Start point

Template

DNA strand

Transcription

factors

5

3

3

5

RNA polymerase II

Transcription factors

3

5

5

3

5

RNA transcript

Transcription initiation complex

Figure 17.8


Unit 3 review

  • The ribosomal subunits

    • Are constructed of proteins and RNA molecules named ribosomal RNA or rRNA

Figure 17.16a


Unit 3 review

Gene 2

DNA

molecule

Gene 1

Gene 3

DNA strand

(template)

5

3

A

C

C

T

A

A

A

C

C

G

A

G

TRANSCRIPTION

A

U

C

G

C

U

G

G

G

U

U

U

5

mRNA

3

Codon

TRANSLATION

Gly

Phe

Protein

Trp

Ser

Figure 17.4

Amino acid

  • The DNA template (gene) determines the order of bases in the mRNA transcribed alongside.

  • mRNA determines the order of Amino Acids during translation


Unit 3 review

3

1

2

RNA transcript (pre-mRNA)

5

Intron

Exon 1

Exon 2

Protein

Other proteins

snRNA

snRNPs

Spliceosome

5

Spliceosome

components

Cut-out

intron

mRNA

5

Exon 1

Exon 2

  • Spliceosomes remove the __ons from pre mRNA

sn = small nuclear

Figure 17.11


Unit 3 review

Know how to use this table to determine which amino acids the mRNA is coding for!


Substitutions

Substitutions

  • A base-pair substitution can cause

    • missense or

    • nonsense


Unit 3 review

  • DNA replication is semiconservative…

    • Each new daughter molecule has one old strand and one newly made strand


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