BIGGGGG SCI SEM 1

DNA

Deoxyribonucleic acid - the chemical compound that carries the inherited information in the cell, codes for protein production

Nucleotide

The basic structural unit of DNA, consisting of a deoxyribose sugar, a phosphate and a nitrogen base.

Gene

A section of DNA, that codes for a particular trait

Chromatin

Highly coiled DNA molecule

Chromosome

Super coiled chromatin (DNA) to form a rod-like structure that contains the genes of an individual

DNA Replication

The process by which a DNA molecule forms an exact copy of itself

Protein

An organic compound made of amino acids that controls chemical reactions in the body

Helicase

Enzyme responsible for separating the two sides of the DNA molecule

DNA Polymerase

Enzyme involved in attaching loose nucleotides to the exposed DNA strand

DNA Ligase

Enzyme involved in repairing the bonds that hold the backbone of the nucleotides together to form DNA

Allele

An alternative form of a gene that occurs at a given point in a chromosome

Dominant

Where one allele masks the effect of the alternative allele

Recessive Alle :3

The allele which is only shown if it is not masked by the effects of a dominant allele :3

Genotype

The genes present in an individual, usually represented by letters eg. RR, Rr, rr

Phenotype

The physical appearance of an individual as determined by its genotype

eg. Tongue rolling and non tongue rolling

Homozygous

Where an individual has two identical alleles for a given gene

Heterozygous

Where an individual has two different alleles for a given gene

Punnett square

A table used to solve genetic problems

Sex-linked trait

A trait controlled by a gene found on a sex chromosome (usually the X chromosome).

X chromosome

One of the sex chromosomes; carries many genes.

Y chromosome

The smaller sex chromosome; carries fewer genes.

X-linked inheritance

When a gene is located on the X chromosome.

Carrier

A person who has one copy of a faulty gene but does not show symptoms.

Affected

A person who shows the trait or disease.

Dominant

A gene that only needs one copy to be expressed.

Recessive

A gene that needs two copies to be expressed (in females).

RAHHH

meow

Pedigree

A diagram that shows how a trait is passed through a family.

Generation

A level in a pedigree (e.g. grandparents, parents, children).

Individual

One person in the pedigree.

Trait

A characteristic that can be inherited.

Inheritance pattern

The way a trait is passed from parents to offspring.

meow meow meow

mew

Cell cycle

The series of stages a cell goes through as it grows and divides.

Mitosis

• The process where one cell divides to make two identical cells

• Cell division where the chromosomes in a cell nucleus are separated into two identical sets of chromosomes, each in its own nucleus

Interphase

The stage before mitosis where the cell grows and copies its DNA.

Chromosome

A structure made of DNA that carries genetic information.

Chromatid

One half of a duplicated chromosome (two identical halves joined together).

Sister chromatids

The two identical copies of a chromosome joined in the middle.

Centromere

The point where sister chromatids are attached.

Cytokinesis

The cell splits into two identical daughter cells.

Daughter cells

The two new cells formed after mitosis (genetically identical).

Nucleus

The part of the cell that contains DNA.

Spindle fibres

Thin structures that pull chromatids apart during mitosis.

Prophase

Chromosomes become visible and the nucleus starts to break down.

Metaphase

Chromosomes line up in the middle of the cell.

Anaphase

Sister chromatids are pulled apart to opposite sides of the cell.

Telophase

New nuclei form around each set of chromosomes.

STAGES OF MITOSIS

• Prophase

• Metaphase

• Anaphase

• Telophase

Meiosis

• A type of cell division that produces four non-identical cells (gametes)

• Cell division that halves the number of chromosomes when forming sex cells

Gametes

Sex cells (sperm and egg).

Haploid (n)

A cell with half the number of chromosomes

Diploid (2n)

A cell with the full set of chromosomes.

Homologous chromosomes

Pairs of chromosomes (one from each parent) that carry the same genes.

Crossing over

When homologous chromosomes swap sections of DNA to increase variation.

Independent assortment

The random way chromosomes are separated into gametes.

Genetic variation

Differences in DNA between individuals.

Fertilisation

When a sperm and egg join to form a new cell.

Zygote

The fertilised egg (diploid cell).

Meiosis I (separates chromosome pairs)

Prophase I

Homologous chromosomes pair up and crossing over occurs.

Metaphase I

Chromosome pairs line up in the middle.

Anaphase I

Homologous chromosomes are pulled apart.

Telophase I

Two cells form, each with half the chromosomes.

Meiosis II (similar to mitosis)

Prophase II

Chromosomes become visible again.

Metaphase II

Chromosomes line up in the middle.

Anaphase II

Sister chromatids are pulled apart.

Telophase II

Four haploid cells are formed.

Trait

An inherited feature of an organism (also called a characteristic)

Theory

An explanation of a small part of the natural world that is supported by a large body of evidence

Evolution

The gradual change in the characteristics of a species over a period of time

Natural Selection

The process by which a species becomes better adapted to its environment

Mutation

A new variation, caused by the permanent change in a gene or chromosome

Variation

The differences that exist between individuals or populations

Selection pressure

The pressure exerted by environmental factors in causing the death of organisms with characteristics not suited to the environment.

Favourable trait

Traits that are suited to the environment and favour the reproductive success of an individual

DNA pt2

DNA = Deoxyribonucleic acid

Carries genetic information

Contained in the nucleus, small amount found in mitochondria.

Capable of SELF-REPLICATION

DNA structure

DOUBLE HELIX - twisted ladder shape

Nucleotides

• the building blocks of DNA

• Consists of a sugar, a phosphate, and a nitrogen base (Adenine, Thymine, Cytosine or Guanine)

sides or backbone of DNA

made up of alternating Sugar and Phosphate molecules

rungs of DNA

• are made up of nitrogen base pairs (A-T or C-G) held together by a hydrogen bond

• the nitrogen base is attached to the sugar molecule of the backbone

Base paring

• aka COMPLEMENTARY BASE PAIRING

• formed by two nitrogen bases joining

• all 4 bases have different chemical structures, which means they can only pair up in one way

number of hydrogen bonds

AT - 2

GC - 3

Where is DNA

• DNA is stored in the nucleus as CHROMOSOMES

Chromosomes

• made up of DNA

• there are 46 chromosomes in every cell arranged in 23 pairs

• they are thin, thread-like structures

• consists of segments of DNA known as GENES.

Genes

• segments of DNA

• The base sequence of each gene contains information for one characteristic - aka GENETIC CODE

what gene do

• they provides the instructions for construction of one particular protein

what protein do

• they control the characteristics and functions of the body

• e.g. Hair and Nails, Hormones, Enzymes

how many gene and stuff (dont need to know prob)

It is estimated that there are about 20,000–25,000 genes in the human genome (i.e. about 3 billion base pairs).

wowie so sugoi!

DNA functions

1. Carrying genetic information for inheritance

2. Coding for amino acids to produce proteins

why DNA replicate

so they can carry the genetic code accurately and be able to pass it onto future generations, every cell must have identical DNA to the original body cell

this why SELF-REPLICATION happens

DNA replication

the process of DNA making an exact copy of itself is known as DNA REPLICATION

Protein Synthesis

• DNA holds the instructions for every protein in the body.

• The process of making proteins in the cell is called PROTEIN SYNTHESIS.

• Proteins are made up of building blocks called AMINO ACIDS.

how we get amino acids

• We get our supply of amino acids from the foods we eat.

• There are 20 amino acids in total.

• A group of three bases on the DNA strand (called a codon) codes for 1 amino acid.

where does protien synthesis occur

• proteins are synthesised at the RIBOSOMES

DNA can not leave the nucleus, so it has to be copied into RNA (ribonucleic acid) which is only single stranded and small enough to leave the nucleus through the nuclear pores. (prob dont need to know)

Protein synthesis process (dont need to know)

• The small RNA molecule leaves the nucleus and goes to the ribosomes (which is the site of protein synthesis).

• The ribosome reads the RNA in groups of 3 bases and signals for the matching amino acid to add to be added to the chain.

• Therefore, the order of bases determine the order of amino acids in the protein.

DNA’s two basic functions

1. Carrying genetic information for inheritance

2. Coding for amino acids to produce proteins

DNA replication 1

Replication starts at specific sequence on DNA

DNA replication 2

Helicase unwinds and unzips DNA, breaking hydrogen bonds that join complementary base pairs, and forming two separate strands

DNA replication 3

In nucleus, there are free nucleotides

DNA replication 4

New DNA built up from the four different nucleotides (A, C, G and T)

DNA replication 5

Nucleotides attach to bases on old strands by complementary base pairing. T base to A nucleotide and G to C

• Each chain acts as a template strand

• Free Nucleotides Bind

DNA replication 6

DNA polymerase joins new nucleotides to each other

DNA replication 7

DNA ligase repairs the bonds that hold the backbone of the nucleotides together to form DNA

DNA replication 8

• The result is that there are two identical DNA molecules

• each with one new synthesised strand of DNA and one strand from the original

Helicase

Enzyme responsible for separating/unzipping the two sides of the DNA molecule

DNA polymerase

Enzyme involved in attaching loose nucleotides to the exposed DNA strand