Mutations Flashcards
(41 cards)
What are mutations?
Any change in the genetic composition of an organism.
Why does a mutation occur
-could occur by chance
-could occur as a result of mutagens
What are mutagens
-physical or chemical agents that cause mutations.
When can gene mutations be transferred to children
Only mutations that occur in the sexual organs can be passed on
What are the 2 types of mutations
-Gene mutations
-chromosomal mutations
What are gene mutations?
-A change in the nucleotide sequence
When can gene mutations occur?
They can occur during:
- DNA replication
- Transcription of DNA and RNA
- Crossing over during prophase of meiosis
What are the four types of gene mutations?
-Substitution
-deletion
-insertion
-inversion
A change in the nucleotide sequence.
As a result…
As a result the code for protein synthesis changes and forms a faulty protein.
What happens in substitution?
-One nitrogenous base is replaced by another
-results in the alterations of one amino acid
-point mutation
What happens in deletion?
-one or more nitrogenous bases are lost
-results in a frame shift
- all base triplets are altered and consequently all the amino acids are
What happens during insertions?
-one or more nitrogenous bases are inserted
-all base triplets are altered and consequently also the amino acids.
-frame shift
How does a chromosomal mutation occur?
- it occurs when Meiosis doesn’t proceed properly which results in changes in one chromosome number or structure.
What is Aneuploidy?
- extra chromosomes or missing chromosomes in a cell.
Give examples of Aneuploidy.
- Down syndrome - 47 chromosomes.
- Turner Syndrome - only one sex chromosomes (XO)
- Klinefelter syndrome- extra sex chromosomes (XXY)
How does Down syndrome occur?
Occurs during the production of eggs during Meiosis when chromosomes number 21 doesn’t separate during Anophase 1
What is a zygote?
It is a fertilised egg cell that is formed when a female gamete and a male gamete join.
What is trisomy 21?
A genetic chromosome 21 disorder causing developmental and intellectual delays.
-Also known as Down syndrome.
What are the characteristics of Down syndrome? (9)
- small almond eyes
- ears situated lower down the head
- flat forehead
- short, stubby toes
- poor muscle tone
- flat nose bridge
- large tongue
- predisposed to heart disease
- mental retardation
What is the Maternal Age Effect?
- After the age of 35 the risk of complications like miscarriage, congenital disorders and high blood pressure.
What gender does the turner syndrome effect and what happens with the chromosomes?
- effects the development of females
- only one X chromosome (XO)
How many people develop turner syndrome?
1 out of 40 zygotes develop turner syndrome
What are the characteristics of turner syndrome? (7)
- abnormal growth - short in stature
- lack of female secondary sexual characteristics.
- sterile
- slight mental retardation
- webbed neck
- heart defects
- low hairline
What are Somatic Mutations.
They are mutations that occur in body cells and are not transmitted to the next generation. It can cause cells to become malignant.
