Genetics and Central Dogma of Molecular Biology

Genetics

is the study of how traits are passed from parents to their offspring

Heredity

is the passing of genetic factors from parent to offspring (or from one generation to the next)

Variation

is the difference between organisms caused by alternate forms of DNA

Dominant Allele

An allele or a gene that is expressed in a organism’s phenotype, masking the effect of the recessive allele or gene when present

Recessive Allele

is a variety of genetic code that does not create a phenotype

Law of Dominance

states that when two alleles of an inherited pair is heterozygous, then the allele that is expressed is dominant whereas the allele that is not expressed is recessive

Law of Codominance

occurs when two versions, or “alleles” of the same gene are present in a living thing, and both are expressed. Instead of one trait being dominant over the other, both traits appear

Law of Incomplete Dominance

refers to a circumstance in which the two copies of a gene for a particular trait, or alleles, combine so that neither dominates the other. This creates a new phenotype or set of observable characteristics caused by the interaction of genetics and environment

Law of Independent Segregation

states that two alleles for each trait segregate, or separate, during the formation of gametes, and that during the formation of new zygotes, the alleles will combine at random with other alleles. This ensures that a parent, with two copies of each gene can pass on either allele

Law of Independent Assortment

states that different genes and their alleles are inherited independently within sexually reproducing organisms. During meiosis, chromosomes are separated into multiple gametes, Genes linked on a chromosome can re arrange themselves through the process of crossing-over

Monohybrid cross

determines the allele combination of offspring for one particular gene only

Step 1

Designate characters to represent the alleles.
Capital letter for the dominant allele, lower case for the recessive allele

Step 2

Write down the genotype and phenotype of the parents
This is P generation (Parental Generation)

Step 3

Write down the genotype of the parental gametes
These will be haploid as a result of meiotic division

Step 4

Use a Punnett grid to work out the potential gamete combinations
As fertilization is random, all combinations have an equal probability

Step 5

Write out the genotype and phenotype ratios of potential offspring
This is the (Fsub1) generation (First filial generation)
Subsequent generations through interbreeding labeled (Fsub2), (Fsub3)

Dihybrid Cross

A cross between two parents that differ by two pair of alleles (AABB x aabb)

Chromosome

is a string of DNA wrapped around associate proteins that give the connected nucleic acid bases as a structure

DNA

also known as deoxyribonucleic acid, is a molecule that contains the instructions an organisms need to develop, live and reproduce. These instructions are found inside every cell, and are passed down from parents to their children

RNA

also known as ribonucleic acid, are single-stranded nucleic acids composed of nucleotides. It plays a major role in protein synthesis as it is involved in the transcription, decoding, and translation of genetic code to produce proteins

Replication

is the process of making an identical copy of a section of duplex (double-stranded) DNA, using existing DNA as a template for synthesis of new DNA strands. In humans and other eukaryotes, this occurs in the cell nucleus

Transcription

is the process of RNA synthesis, controlled by the interaction of promoters and enhancers. Several types of RNA are produced, including messenger RNA (mRNA), which specifies the sequence of amino acids in the protein product, plus transfer RNA (tRNA) and ribosomal RNA (rRNA), which play a role in the translation process

Initiation

the DNA molecule unwinds and separates to form a small open complex. RNA polymerase binds to the promoter of the template strand.

Elongation

RNA polymerase moves along the template strand, synthesising and mRNA molecule

Termination

in prokaryotes there are two ways in which transcription in terminated. In Rho-dependent termination, a protein factor called “Rho” is responsible for disrupting the complex involving the template strand, RNA polymerase and RNA molecule

Translation,

after transcription the RNA molecule is processed in a number of ways: introns are removed and exons are spliced together to form a mature mRNA molecule consisting of a single protein-coding sequence

Reverse Transcription

is a technique used by researchers to generate a complementary strand of DNA (cDNA) from RNA. The technology is based on a retroviral mechanism whereby the enzyme reverse transcriptase can reverse transcribe RNA into DNA. This is especially helpful when scientist only have tissue and want to study gene sequence