IB biology HL: Gene expression D2.2

difference between gene expression and cell differentiation

• different gene expressions lead to cell differentiation

• as different genes are expressed, Ie different proteins are synthesised

transcription factors

proteins that help control the transcription of genes by binding to nearby non coding regions of the DNA

enhancer sequence

short regions of DNA that can be bound by transcription factors to increase the likelihood of gene transcription. They can be far from the area that they promote. they are non-coding DNA

promoter sequences

DNA region where transcription is initiated, responsible for starting the process if copying a gene’s DNA sequence into an RNA molecule

gene expression

the way that information in the genes which has an effect on the phenotype

regulation

the act if controlling or directing a process or system

the act if controlling or directing a process or system

broken down by nuclease enzymes, which need to be regulated

Methylation

Methylation is addition of methyl group. Addition of methyl to cytosine group of a promoter represses transcription and addition of methyl tp amino acids of histones can cause transcription to be repressed or activated.

Epigenesis

gene expression can be affected by the environment. Genome is unchanged by different phenotype. The transcriptome us changed by epigenetics

methylation

can happen to actual DNA, or to histone proteins

epigenetics

The study of heritable changes in gene activity that are not caused by changes in DNA base sequences. Examples are DNA methylation or histone modification

genotype

the combination of alleles inherited by an organism

epigenetic inheritance

epigenetic changes, which were taught to not be inheritable, can be if epigenetic changes, such as DNA methylation or histone modification remain in place during mitosis

environmental effects in gene expression example

alteration of methyl tags in DNA as a response to air pollution

epigenetics: imprinting

• epigenetic tags on ovum and sperm cell

• so one copy of the gene might be turned on and the other turned off ( from both parents)

• so in imprinting only one of the genes will be expressed

epigenetics, imprinting, tigersxlions

male lions pass on genes to encourage growth, while female lions pass on genes to discourage growth

tigers don’t have anything like that

male tiger x female lion = tigon. Smaller than parents as male tiger doesn’t have imprints to encourage growth and counteract mother

male lion x female tiger = liger. Even bigger than parents, as female tiger doesn’t have imprints to counteract growth imprints of male.