ATAR Human Bio - Mutations

germline mutations

• occurs in the gametes (egg or sperm)

• passed on to offspring, so every cell in the child will carry it

• can be a gene mutation or chromosomal mutation

somatic mutations

•   occurs in body cells & can not be passed on

•    only affects some cells in the person

• can be a gene or chromosomal mutation, but stays in that individual.

gene mutations

• changes in only a single gene in DNA

• affects only one protein/amino acid

• involves substitution, insertion or deletion of nucleotide bases

chromosomal mutations

• changes in multiple genes in DNA

• affects all or part of a chromosome

• involves deletions, duplications, inversions, translocations, and non-disjunction

• usually cause severe abnormalities

substitution

one base is swapped for another base

insertion

a new base is added to the DNA sequence

deletion

an exciting base is removed from the DNA sequence

silent

base sequence changes & protein still codes the same amino acid

missense

base sequence changes & protein codes for a different amino acid

nonsense

base sequence changes & protein codes for a stop codon. a shorter protein is produced that cannot fulfil its function

deletion

a selection of chromosome is lost/removed

duplication

a section of chromosome is repeated

inversion

a broken section of chromosome reattaches itself upside down

translocation

a section of chromosome moves to a different chromosome

trisomy

the addiction of an extra chromosome into a daughter cell. this happens due to nondisjunction during meiosis.

down syndrome (trisomy 21)

• occurs when a when a person has an extra chromosome 21.

• symptoms include: intellectual disability, facial differences, heart defects

patau syndrome (trisomy 13)

• occurs when a child has an extra chromosome 13

• symptoms include: severe intellectual disability, small head, cleft lip, extra fingers

monosomy

when an individual is missing a chromosome, only having one copy instead of two. most cases usually lead to a miscarriage.

cri du chat Syndrome

• part of chromosome 5 is missing

• the child has a cry sound like a cat due to problems with nervous system and larynx

• also will have slowed physical and mental development

Turner’s syndrome

• a female has only one X chromosome (XO)

•  these females are short in stature, lack secondary sex characteristics and are infertile

• since they do not have a Y chromosome, they are biologically considered to be a female