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The Body Code [Alicia Shen] (What is DNA? (The Discovery of the Double…
The Body Code [Alicia Shen]
Chemical Structure
Nucleotides
Sugar-phospate backbone
Deoxyribose sugar molecule
Phosphate group
Nitrogenous Bases
Adenine
Thymine
Guanine
Cytosine
What is DNA?
Present in the nucleus of all cells in all organisms
Controls chemical changes that occur in cells
Controls the type of organism produced
The Discovery of the Double Helix
Watson and Crick
Rosalind Franklin
Photo 51
Double helix (like a twisted ladder)
Sexism in science
Maurice Wilkins
Deoxyribonucleic acid
"deoxyribose"
Sugar
"nucleic acid"
Type of biomolecule
Double-helix, double stranded
Found in the nucleus
Proteins
Main functions
Growth
Chemical messengers
Enzymes
Energy
Transport
Immune response
Regulation of fluid and acid-base balance
Protein Synthesis
Transcription (1)
Occurs in the nucleus
RNA Polymerase connects complimentary bases
This forms mRNA
mRNA moves into cytoplasm
Ribosomes are made of rRNA
mRNA connects to ribosome
Translation (2)
tRNA molecules carry amino acids and are in the cytoplasm
tRNA transfers amino acids to complimentary bases
tRNA reads in triplets- codons
AUG is typically the start codon (methionine)
Amino acids are help together by a peptide bond
Genes & Chromosomes
Chromosomes
Sex Chromosomes
Females have XX
Two of the same chromosome
Males have XY
Sex determination depends on the male
Dominant/recessive traits
XX provides a backup
Intersex
XXY/XYY/X
Autosomes
We can see chromosomal abnormalities in karyotypes- one extra or one less chromosome
Nondisjunction
The failure of homologous chromosomes to separate properly during cell division
Genes
Functional parts of DNA
Provide instructions for proteins
Proteins are needed to perform a job in the cell
Functional product
Alleles (uh-leel-s)
Various forms of genes/genetic codes
Dominant/Recessive
Brown/black hair is dominant
Blonde hair is recessive
The dominant trait will always be expressed
Genotype
The set of alleles of a gene an individual carries
Homozygous (AA/aa)
Heterozygous (Aa)
Phenotype
Physical expression
Observable characteristics of a specific trait
Homozygous
Heterozygous
Diploid organism with cells containing different alleles (one wild-type and one mutant)
RNA vs. DNA
Similarities
Nucleic acids
Both have 4 bases
3 common bases
Adenine, Guanine, Cytosine
Differences
DNA is double stranded whereas RNA is single stranded
RNA has Uracil as a base instead of DNA's Thymine
RNA
Ribonucleic acid
"ribose"
Sugar
Starts in the nucleus, then travels out
3 types
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
The Central Dogma of Genetics
"From DNA to Protein"
Cell contains the nucleus which contains the genome
The genome is split between 23 pairs of chromosomes
Chromosomes consist of DNA tightly packaged around histones
Genes hold instructions for making proteins
Transcription
When a gene is switched on, RNA polymerase attaches to the start of the gene and moves along the DNA
It creates a strand of mRNA out of free bases in the nucleus (DNA code determines the order in which bases are added)
1 more item...
DNA (gene)
transcription (nucleus)
RNA (message)
translation (cytoplasm)
polypeptide (product)
Cells
Somatic Cells
Diploid
Contains 46 chromosomes
Sex Cells (gametes)
Haploid
One copy, only 23 chromosomes
Female Reproductive System
Egg (X)
Found in ovaries
Cervix, Uterus, Vagina, Ovary, Fallopian Tube
Fertilisation (Conception)
The Cycle
Brief Overview
Week 1
Period
Week 2
Ovulation (5 hours)
Cervix opens; sperm swim in
Sperm travel through the cervix and uterus into the fallopian tube, then travelling to the ovary
Week 3
Sadness
Week 4
PMS (Premenstrual Syndrome)
The Race to Life
Millions of sperm are deposited in the vagina at the point of ejaculation; the sperm swim up into the fallopian tubes
The sperms that succeed in reaching the egg will attach itself to the ovum, but only one should succeed in penetrating it
Enzymes in the head of the sperm are used to break down the cell membrane of the ovum
Fertilisation occurs when a sperm meets an egg in the fallopian tube/oviduct (takes 30 minutes)
Within hours of conception, the zygote undergoes cell division
A ball of cells will be formed- this is the embryo
Within the first week, the embryo embeds itself in the uterus lining (endometrium) and continues to develop/grow
Progesterone (hormone) prevents eggs from being produced
Most of the sperm will be killed along the way
Zygote = fertilised egg/fused gametes
two haploids combine to create a diploid (zygote)
Homologous pair
Twins
2 eggs released
Semi-identical
1 egg fertilised by 2 sperm
less than 1% of twin population
Male Reproductive System
Sperm (X/Y)
Produced in testes through chemical signalling of testosterone
DNA in the head of sperm
Each ejaculate = 40 million sperm
Testis, Penis, Urethra, Scrotum, Vas Deferens, Prostate Gland, Seminal Vesicle
Variation
Differences between individuals of the same species
Due to genetic and environmental causes
This is stored in genes which reside in the nucleus
Pedigrees
There are 4 types of inheritance disorders
Autosomal disorders
Happen on the autosomal chromosomes (not on the X or Y)
Autosomal Dominant
Just one faulty alleles will express the disorder
An affected parent has a 50% chance of passing the genetic disease to their offspring
Those affected can be heterozygous or homozygous (Aa or AA)
Condition is found in each generation
Autosomal Recessive
Both alleles are faulty and recessive
Not living with the disorder but carrying the gene
If parents are both carriers, there is a 1/4 chance of having an affected child
Condition tends to skip a generation
Genetic Engineering
Extracting genes from one organism and inserting it into the DNA of another (transgenic)
Can be done to bacteria, plants, and animals
Used by scientists to enhance or modify the characteristics of an individual organism
It has agricultural and medical uses (creating human insulin, higher yield crops)
Diabetes
Type 1 and Type 2
Patients need insulin injections
Insulin Production
The genetically modified bacteria asexually reproduces; mass production of insulin occurs
A plasmid is a small, circular ring of DNA found in bacteria
A small section of the plasmid is cut out by restriction enzymes
The gene that produces insulin is put in the gap in the plasmid
Cloning
Donor cells taken from nucleus donor
Egg cell removed from egg cell donor
Enucleate the egg cell so that it becomes a haploid casing
Electro-cell manipulator triggers mitosis- fertilisation
Insert donor nucleus (diploid nucleus) in haploid casing
Insert into surrogate mother