genes and health and enzymes and nucleic acid

What presses down and covers the opening of the trachea

Epiglottis

Protective layer found in the outer layer of the lungs

Pleural membrane

What happens mechanism wise when inhalation takes place

Ribcage up and out

Intercostal muscle contract

Diaphragm contracts

What happens mechanism wise when exhilation takes place

Increase volume in chest cavity - lower the atmospheric pressure

Air flows into lungs (to a lower pressure)

Composition of inhaled air

O2 - 21

Co2 - 0.03

N2 - 78

Composition of air exhaled

O2 - 16

Co2 - 4

N2 -78

Is inhalation active or passive

active

Is exhalation active or passive

Passive

Role of cilia and mucus

1. Pathogens trapped by mucus

2. Cilia sweeps the mucus to the back of the throat

3. Mucus is swollen

4. Mucus enters stomach and pathogens are killed by stomach acid - hcl

What does the goblet cell so

Secretes mucus

Name of bottom membrane in CFTR channel

Basal

Name of top membrane in CFTR channel

Apical

Normal mechanism of ciliated epithelial membrane - Response to dry mucus following exercise

1. Cl- pumped across basal membrane into epithelial cell (at)

2. Cl- diffuse across the apical membrane through CFTR protein from higher Cl- to a lower Cl- (fd)

3. The mucus now has higher solute conc than cell (hypertonic)

4. H2o diffuses into mucus by osmosis ensuring mucus is runny

Cystic fibrosis - CFTR protein channel does not work

CFTR cannot move Cl- across the apical membrane

Na+ channel allows Na+ to diffuse into the epithelial cell

The inside of the epithelial cell becomes hypertonic higher solute concentration

Water diffuses from the mucus into the epithelial cell by osmosis

The mucus becomes thick and sticky

Mucus is too thick and sticky

Mucus is too thick ti be moved by cilia and blocks ducts in the body

Functions of proteins

Transport

Catalyst

Hormones - chemical messengers - communication

Structure

Defence - antigen - antibodies

Muscle contraction

What elements are found in protein

Carbon

Hydrogen

Oxygen

Nitrogen

Primary structure of protein

Proteins are polymers built up from units called amino acids

What amino acid is formed in protein when r side group is - H

Glycine

What amino acid is formed in protein when r side group is - CH3

Alanine

What amino acid is formed in protein when r side group is - C3H6

valine

What amino acid is formed in protein when r side group is - CH2SH

Cysteine

R group in protein

Variable group

R group can be polar/non polar

They give amino acids specific properties

Gene

Length of dna containing a small part of a genetic code

Sequence of bases that code for specific proteins

How do genes control living organisms

Genes code for

Amino acids

Establish bonding between R group

Fold into secondary and Tertiary structure

Final Shape

Specific function/role

Structure of nucleic acids

Includes dna and rna

Both made of nucleotides

Nucleic acid molecules are made up of thousands and thousands of nucleotides

Three components of nucleotides

1. Ribose sugar (deoxyribonucleic acid)

2. Phosphate group

3. Nitrogen base - A G C T

How are the three components of nucleotides joined

Condensation reaction

How do 2 nucleotides bond

Phosphate group and the sugar bind

Condensation reaction

How many base pairs in a complete turn of the helix

10

What forms the sides of the dna double helix ladder

Alternating deoxyribose sugar units

What forms rungs

Bonded pairs of bases

How are the two strands of DNA held together

Hydrogen bonds

How many hydrogen bonds between guanine and cytosine

3

How many hydrogen bonds between adenine and thymine

2

Function of dna

To code for the production of specific proteins during protein synthesis

Dna adaptations

Sugar phosphate - very stable and on the outside of the molecule - protecting the code

Strands attached by h bonds - can be broken to allow rna replication

Contains bases - sequence of bases is the genetic code and determines protein synthesise and what amino acids are coded for resulting in a specific proteins

How many different amino acids

20

Differences between RNA and DNA

RNA

Contains ribose sugar

Is single stranded

Nucleotide contains vracil base

What base do dna nucleotides contain

Thymine

Triplet code

Every 3 bases code for specific amino acid

Degenerate

There is more than one triplet sequence (codon) to code for an amino acid

Non over lapping

Every triplet is discrete (only use one)

Dna full name

Deoxyribose nucleic acid

Rna full name

Ribonucleic acid

When does dna replication

During the interphase of the cell cycle

Before the start of mitosis and meiosis

What does it mean that dna replication is semi conservative

Each new copy of DNA has one new strand and one original strand

Requirements for semi-conservative replication

Original dna

Three dna nucleotides (A T G C)

Dna helicase (enzymes)

Dna polymerase (enzymes)

When does DNA replication begin

When the enzyme DNA helicase unwinds and separates both DNA strands

Stage one of dna replication

Dna helicase breaks the hydrogen bonds between the complementary bases and the 2 strands separate

Stage 2 of dna replication

A - The free dna nucleotides blind with the in-complementary bases complementary base pairing forming h bonds with the original strand

B - the dna polymerase catalyses the formation of phosphodiester bonds to form the new dna strand

Stage 3 of DNA replication

Two identical dna molecules are formed

Each molecules is 50% original and 50% new dna

Replication is therefore semi - conservative

Three steps of protein synthesis

Transcription

Splicing

Translation

Transcription overview

In nucleus

Production of mRNA strand

Pre mRNA molecule is synthesised from part of a DNA molecule

Transcription

1. Dna helicase breaks the hydrogen bonds between the nucleotides and the dna strand divides

2. RNA polymeraise moves along the DNA strands causing the free RNA nucleotides line up next to their complimentray dna bases and match up G-C A-U

3. The RNA polymerase catalyses the formation of phosphodiester bonds to join the nucleotides together until it reaches a sequence programmed to stop transcription at the stage the strand of pre-mRNA is complete

4. Every three nucleotides is referred to as a codon, a strand of pre-mRNA is therefore made up of a sequence of codons

Splicing

Dna is made up of 2 types of sections

Exons - express protein

Introns - ‘junk dna’ - dosent code for proteins

During splicing introls are spliced using the enzyme called splicedsomes

So mRNA is made entirely of exons

The new mRNA is able to move through nuclear pores and enter the cytoplasm

Here it located a ribosome which can be found free in the cytoplasm or attached to the rer

When attached it is ready to start the second phase of protein synthesis

Splicing overview

In nucleus

Pre mRNA molecule is modified by

Removal of introns

Translation overview

On ribosomes

Production of an amino acid sequence/polypeptide

Translation

Process in which the mRNA strand is used as a template for tRNA molecules

Each tRNA carries an amino acid

These amino acids link up in a particular order to form a polypeptide

The ribosome becomes attached to the start codon at one end of the mRNA

tRNA with its complementary anticodon sequence attaches to the mRNA codon and an amino acid (methionine) is released

The released amino acid binds to the previously released amino acid, in this case methionine

Peptide bonds are formed

Energy in the form of ATP is required for this process as well as an enzyme to reduce the activation energy

Each ribosome has the capacity to allow 3 tRNA molecules to bind at any one time

Once the third tRNA molecule attaches, the first tRNA molecule must dislodge from the ribosome and move into the cytoplasm to pick another amino acid

The ribosome continues to move along the mRNA strand (15 amino acids per second) and the process continues until it reaches a stop codon

At this point the ribosome mRNA and tRNA disconnect and the polypeptide chain is complete

mutation

A chain in the base sequence which results in a change to the amino acid sequence

types of mutation

point

Frameshift

point mutation

substitution of base

Frameshift mutation

Addition or deletion of base

what happens to the polypeptide if a frameshift mutation occurs

every amino acid past the point of base addition or deletion is altered

which type of mutation has a greater effect on the protein structure

frameshift

4 types of point mutations

silent

Neutral

Nonsense

Mis-sense

silent mutation

a base is substituted but the new triplet code codes for the same amino acid

This is due to the code being degenerate

Neutral mutation

a substitution/change in the base sequence results in a new amino acid which has similar properties

The bonding relationships are very similar so the tertiary and function of the protein is unaltered

nonsense mutation

a substitution/change in the base sequence results in a stop codon

The resultant protein is shorter so the tertiary structure and function of the protein are different

Mis-sense codon

A substitution/change in the base sequence results in a new amino acid which has different properties

The bonding relationships are very different so the tertiary and function of the protein are different

Mis-sense exam question overview

1. Change in base sequence

2. Change in amino acid sequence

3. Different sequence of r groups changes the bonding relationships

4. Change in secondary and tertiary structure of protein

5. Change in function e.g. change in shape of active site means the enzyme and substrate are no longer complementary

6. No enzyme substrate complexes are formed

Allele definition

A different form that a gene can take

Alleles

The genes controlling each characteristic

Act in pairs

1 from male and 1 from female

Genotype

The genetic make-up of the organism i.e. what alleles are present

Represented by 2 people

Phenotype

The physical appearance of a characteristic

Homozygous

When the alleles from both parents are the same

The organism is said to be homozygous for that characteristic

Heterozygous

When the alleles are different the organism is said to be heterozygous for that characteristic

Recessive allele definition

The recessive characteristic only shows up in the homozygous condition

Dominant allele definition

One 1 allele must be present for the trait to be expressed

Pedigree diagrams

Show the inheritance of genetic diseases over a number of generations

Incomplete dominance

When one allele does not complete dominate

This results in a new phenotype

Results in a blend of alleles

Genetic screening

Can be carried out during fetal development or on newborn babies

assessed by benefit to cost ratio

Amniocentesis

Removing amniotic fluid

Uses a needle, syringe and ultrasound

Occurs during the 16th week

Fetal epithelial (skin) and blood cells are removed

Removed cells are cultured for 2 weeks before DNA is analysed

Negatives

Results not ready until late in pregnancy

Traumatic decision

Risk of false positive and negative

Chorionic villus sampling (CVS)

Removal of corium (placental tissue)

10-14 weeks

Through cervix or abdomen

Takes a few mins

Earlier results

Miscarriage

1 to 2 days recovery

Risk of false positive or negative

Paternal chromosomes inactivated in female placental cells so some diseases not identified

Blood test for genetic testing

No risk of miscarriage

Analysing dna fragments in mothers blood plasma

Small amounts of cell-free fetal dna detectable at 4-5 weeks

analysed at 7-9 weeks

Improving all the time to detect more genetic mutations

Used for single gene disorders

Preimplantation genetic disorders

Ivf takes place to produce embryos

All embryos genetically screened

Only healthy embryos implanted or transferred into uterus

Success rate are low (30%) same as IVF

No chance of miscarriage

Can remove allele from future generations s heterozygotes not implanted

Rights and duties

Based on human rights and duties towards people

Utilitarianism

Maximising the amount of good in the world

Normal absolutes e.g. is killing always wrong

Autonomy

Making decisions for yourself informed consent

Can i make the decision?

Acting virtuously

Justice, prudence, temperance, fortitude, faith, hope and charity