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Completing and Targeting the Functional Protein. Polypeptide chains Undergo modifications after the translation process After translation Proteins may be modified in ways that affect their three-dimensional shape. Proteins.

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Completing and targeting the functional protein
Completing and Targeting the Functional Protein

  • Polypeptide chains

    • Undergo modifications after the translation process

  • After translation

    • Proteins may be modified in ways that affect their three-dimensional shape


Proteins
Proteins

  • An organism's proteins are the machines that make it work, that make it alive.

  • Generally speaking, when there's any problem with those proteins, there'll be a problem with the whole organism


Protein folding

Protein Folding

Protein folding is the process by which a string of amino acids (the chemical building blocks of protein) interacts with itself to form a stable three-dimensional structure during production of the protein within the cell.


Folding
Folding

  • Occurs because attractions and repulsions between atoms.

    Four levels of protein structure:

    1°sequence of amino acids in polypeptide chain

    2° formed by the hydrogen bonds between amino groups

    3° 3-D shape forms-shape due to R-group interaction

    4° occurs only if different polypeptide units form


Misfolded proteins
Misfolded Proteins

  • Sent back to the cytoplasm

  • Tagged

  • Destroyed

  • Misfolded proteins not destroyed can cause disease


Disorders of protein folding
Disorders of Protein Folding

  • Alzheimer

  • Lou Gehrig’s

  • Huntington disease

  • Parkinson

  • Cystic Fibrosis

  • Sickle Cell


Cystic fibrosis
Cystic Fibrosis

  • Protein prevented from going to the plasma membrane

    • Were it controls the flow of chlorine ions

  • Builds up in the cells

  • Causes abnormal chloride channels in cells lining the lungs

    • Buildup of extremely thick mucous

      Inherited disease –Autosomal recessive

      -parents are carriers


Sickle cell disease
Sickle Cell Disease

  • Beta globin gene

  • Valine amino acid replaces glutamic acid

  • Has aggregated hemoglobin molecules

    • Causes bending of the RBC

      • Forming a sickle-shaped

        Inherited disease –Autosomal recessive

        -parents are carriers


Protein collagen
Protein Collagen

  • Major component of connective tissue

    • Ehlers-Danlos syndrome

      • Stretchy skin


Alzheimer
Alzheimer

  • One form- autosomal dominant

  • Protein that monitors storage or use of beta amyloid

  • Causes increase levels of protein


Inheritance
Inheritance

  • Recessive allele

    • expression is masked by another

  • Dominant allele

    • A gene expressed/even one copy

  • Autosomal

    • A chromosome that does not have a gene that determines sex

      Recessive


Autosomal recessive inheritance
Autosomal Recessive Inheritance

  • Affected individuals have a homozygous recessive genotype

  • Cystic fibrosis (cc)

  • Heterozygotes – carriers (Cc)


Genetics problem
Genetics Problem

  • Man with sickle cell disease

  • Has unaffected parents

  • Sister is healthy/husband no family history

  • Sister wants to know the risk that her children will inherit the allele for sickle cell

  • What is the probability


  • 1st pedigree

  • 2nd punnett square

  • Risk she is a carrier

  • If she is a carrier what is the chance

  • Probability – product rule

    • Calculate the overall risk

    • Multiply the probability carrier - if so- will pass to child (two events – one depends on the other)


Chromosomal basis of inheritance

Chromosomal Basis of Inheritance

Genes reside on chromosomes.

Sex Chromosomes and Autosomes

Sex chromosomes contain genes that determine an organism’s sex (gender).

The remaining chromosomes that are not directly involved in determining the sex of an individual are called autosomes.



Chromosomal inheritance
Chromosomal Inheritance

  • Sex Determination

    • In mammals, an individual carrying two X chromosomes is female.

    • An individual carrying an X and a Y chromosome is male.

    • Sex chromosomes pair during meiosis I. Meiosis proceeds, paired chromosomes separate = move to different cells.

      • Sperm has equal chance getting X or a Y chromosome

      • Egg only gets an X


Sex chromosomes
Sex chromosomes

  • Male mammals, Y chromosome contains a gene called – SRY

    • Sex-determining Region Y

    • Codes for protein that causes the gonads of embryo to develop as testes.

    • Females don’t have SRY gene – develop ovaries


Effects of gene location
Effects of Gene Location

  • Sex-Linked Genes and Traits

    • Genes found on the X chromosome are X-linked genes.

    • A sex-linked trait is a trait whose allele is located on a sex chromosome.

    • Because males have only one X chromosome, a male who carries a recessive allele on the X chromosome will exhibit the sex-linked trait.


XaY

XAXA

A father with the disorder will transmit the mutant allele to all daughters but to no sons. When the mother is a dominant homozygote, the daughters will have the normal phenotype but will be carriers of the mutation.

(a)

Sperm

Xa

Y

XAXa

XAY

Ova

XA

XAYa

XAY

XA

(b)

If a carrier mates with a male of normal phenotype, there is a 50% chance that each daughter will be a carrier like her mother, and a 50% chance that each son will have the disorder.

XAXa

XAY

Sperm

XA

Y

XAXA

XAY

Ova

XA

XaY

XaYA

Xa

(c)

If a carrier mates with a male who has the disorder, there is a 50% chance that each child born to them will have the disorder, regardless of sex. Daughters who do not have the disorder will be carriers, where as males without the disorder will be completely free of the recessive allele.

XAXa

XaY

Sperm

Xa

Y

Ova

XAY

XA

XAXa

Xa

XaYa

XaY

Figure 15.10a–c

  • Sex-linked genes

    • Follow specific patterns of inheritance


  • Some recessive alleles found on the X chromosome in humans cause certain types of disorders

    • Color blindness

    • Duchenne muscular dystrophy

    • Hemophilia


Inheritance of sex linked genes
Inheritance of Sex-Linked Genes

  • Muscular dystrophy

    • Absence of a key muscle protein – dystrophin

    • Gene locus on the X chromosome

  • Hemophilia

    • Sex-linked recessive disorder

    • Absence of one or more proteins used for clotting


Concept 15.4: Alterations of chromosome number or structure cause some genetic disorders

  • Large-scale chromosomal alterations

    • Often lead to spontaneous abortions or cause a variety of developmental disorders

  • Chromosome Mutations

    • Chromosome mutations are changes in the structure of a chromosome or the loss or gain of an entire chromosome.

  • Gene Mutations

    • Gene mutationsare changes in one or more of the nucleotides in a gene.


Abnormal chromosome number

Meiosis I cause some genetic disorders

Nondisjunction

Meiosis II

Nondisjunction

Gametes

n  1

n + 1

n + 1

n –1

n + 1

n – 1

n

n

Number of chromosomes

(a)

(b)

Nondisjunction of homologous

chromosomes in meiosis I

Nondisjunction of sister

chromatids in meiosis II

Figure 15.12a, b

Abnormal Chromosome Number

  • When nondisjunction occurs

    • Pairs of homologous chromosomes do not separate normally during meiosis

    • Gametes contain two copies or no copies of a particular chromosome


Alterations of chromosome structure
Alterations of Chromosome Structure cause some genetic disorders

  • Breakage of a chromosome can lead to four types of changes in chromosome structure

    • Deletion

    • Duplication

    • Inversion

    • Translocation


A cause some genetic disorders

F

H

B

C

G

C

D

F

G

B

A

E

H

E

Deletion

(a) A deletion removes a chromosomal

segment.

C

E

B

C

D

A

C

D

F

G

F

H

B

A

E

H

B

G

Duplication

(b) A duplication repeats a segment.

B

A

D

A

C

D

E

F

G

H

G

C

B

E

F

H

Inversion

(c) An inversion reverses a segment within

a chromosome.

(d) A translocation moves a segment fromone chromosome to another,

nonhomologous one. In a reciprocal

  translocation, the most common type,

nonhomologous chromosomes exchange

fragments. Nonreciprocal translocations

also occur, in which a chromosome

transfers a fragment without receiving a

fragment in return.

A

B

M

C

D

G

E

F

G

H

N

O

C

D

E

F

H

Reciprocal

translocation

M

N

A

O

P

Q

R

B

P

Q

R

Figure 15.14a–d

Alterations of chromosome structure


Chromosome structure
Chromosome structure cause some genetic disorders

  • Cri-du-chat syndrome

    • deficiency in segment of the short arm chromosome 5 Missing; with one normal 5


Gene location
Gene location cause some genetic disorders

  • Linked Genes

    • Pairs of genes that tend to be inherited together are called linked genes.

  • Chromosome Mapping

    • The farther apart two genes are located on a chromosome, the more likely a cross-over will occur.

    • Researchers use recombinant percentages to construct chromosome maps showing relative gene positions.


Gene technology copying dna
Gene Technology Copying DNA cause some genetic disorders

  • DNA identification

    • 1) isolate

    • 2) make copies

    • 3) sort by size, compare (unknown w/known)

      PCR

    • Polymerase Chain Reaction

      Technique used to quickly produce small amounts of DNA fragment

      Gel Electrophoresis

      sorts DNA by size (DNA fingerprint)


Genetic engineering
Genetic engineering cause some genetic disorders

  • Modification of DNA

    • Change a single nitrogen base

    • Cut out an entire gene and insert a new one

  • All modifications of DNA code

    • The production of rDNA (recombinant DNA)

      • Pieces of DNA cut and pasted together

        New DNA are formed, new genes, new proteins


Recombinant dna
Recombinant DNA cause some genetic disorders

  • Insulin

  • Growth hormones

  • Clotting factors

  • These are techniques of DNA technology used to modify the genome of a living organism

    • Genome – complete genetic material contained in an individual


Human genome project
Human Genome Project cause some genetic disorders

  • Research effort to sequence all of our DNA

  • Locate within it all of the functionally important sequences, such as genes.

  • Applications

  • Discovery of specific genes responsible for several genetic disorders

    • Cystic fibrosis

    • Muscular dystrophy

    • Colon cancer


Genomics
Genomics cause some genetic disorders

  • 3 billion letters of the human genetic code have been sequenced

  • Bioinformatics

    • Biological science

    • Computer science

    • Information technology

    • BLAST – data base for storage of genes in different organisms


Genomics1
Genomics cause some genetic disorders

Proteomics

  • The study of all the proteins

  • Proteins encode

    • Carry out the work in the cell

      Bioinformatics can search DNA sequence/ match specific gene with a protein

      Microarrays

      two-dimensional arrangement of DNA/cloned genes

      show which genes are active in a cell

      used to classify cancers


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