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- changes that affect the entire chromosome and their genes, not only specific nucleotides
- mutations come from inconsistencies and errors in the process of cell division which is the cause to a part of a chromosome being duplicated, breaking off, or being transferred to another chromosome

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What is mutation?
-Permanent change in the dna of an organism.

-May occur in body cells or gametes cells.

What causes Gene Mutation?
-Mutations can occur befcause of factors in our environment such as smoking or UV light, these are called mutagens

3 TYPES OF GENE MUTATION

(will be explained in detail later on)

-Substitution
+Point mutation
-Insertion
+Frameshift mutation
-Deletion
+Frameshift mutation

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-Is a mutation in which one nucleotide is substituted for another.
-A point mutation is a large category of mutations that occurs when a single base pair is changed (substitution), added (insertion), or disappeared (deletion) in the nucleotide sequences of DNA and RNA.
-Point mutations affect the production, composition, and function of the encoded protein downstream, which consequences can range from no effect to deleterious effects.

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-Point mutations mainly occur during DNA replication.
-DNA replication is the process of creating two new single-stranded DNAs based on double-stranded DNA. Existing double-stranded DNA is separated into single strands, and complementary strands are synthesized by each acting as a template. At this time, if the DNA is synthesized incorrectly and this is not corrected by the repair mechanism, the faulty strand is used as the next template, causing mutation.

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There are 4 types of Chromosomal Mutation:

Duplication
-A heterozygous duplication resulting in an extra copy of some regions on the chromosome
Deletion
-Where sections of a chromosome detach and disappear
Inversion
-Which is when two points in a chromosome breaks and twists itself 180 degrees then rejoining with the original Chromosome
Translocation
-When a piece of a chromosome breaks off and attach's to another chromosome

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- Extremely lethal to any haploid, gametes or have serious consequences genomic imbalance in cells.
- The severity increases depending on the size of the deletion.
- Another potential source of damage is that any recessive, deleterious that are in the normal counterpart of the deleted region will be expressed in the phenotype which can be damaging
EX: cri - du - chat syndrome which is where a section of a certain chromosome removes germinal tissues (the earliest stage in developing a baby) causing several birth defects such as intellectual disability and an abnormally small head.

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Further split
- Paracentric inversions do not include the centromere, and both breaks occur in one arm of the chromosome.
- Pericentric inversions include the centromere, and there is a break point in each arm.

Inversion can then have different effects such as harmful effects, if a chromosomal break occurs within an essential gene and, position effect where purpose of a gene is changed by its relocation.

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The yellow section is duplicated again making two of the same as seen on the right.

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- Can occur during crossing over or by meiotic irregularities.
- If the duplication becomes a homozygous it opens the door for genetic variation allowing for new genetic functions through mutations within the duplicate copy.

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A heterozygous translocation which has a full set of genes and can be used unless one of the breaks causes damage to a gene or if there is a position effect.

During Meiosis, half of the daughter cells have deletions in certain chromosome regions that changed positions and half of the products are duplicated for the other.

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- occurs when 1 or more homologous chromosomes don’t separate during anaphase of meiosis.
- results are gametes that do not have the same number of chromosomes, and could either have more or fewer chromosomes than the parent cell
- examples: human disorders including Down syndrome (trisomy 21), Klinefelter disorder (extra X chromosome in cells of males), and Turner syndrome (females have 1 X chromosome)

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- HbS: sickle cell anemia allele trait/disease - on a recessive allele of a hemoglobin gene, meaning the person has required 2 copies of the recessive allele, 1 from both parents (this will not occur in a person with both dominant and recessive copies of the allele
- this trait can be passed from parents to the offspring
- the will or won’t of occurring in the offspring depends on which kind of cell the mutations happens in
- the transmitted mutation could or could not affect the phenotype and physical expression of a trait in the person

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Illustration of three types of point mutations to a codon.

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Illustration of three types of point mutations to a codon.

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Silent-  A form of point mutation resulting in a codon that codes for the same or a different amino acid but without any functional change in the protein product.

Nonsense-  A point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product.

Missence-  When the change of a single base pair causes the substitution of a different amino acid in the resulting protein.  This amino acid substitution may have no effect, or it may render the protein nonfunctional.

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Explanation and the result of substitution mutations

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Explanation and the result of substitution mutations

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A type of replication error during DNA replication which places the wrong nucleotide or sequence of nucleotides in the wrong position.
A type of substitution mutation= A point mutation

Result- A substitution mutation results in DNA of the same length. It does not add or subtract from the number of nucleotides in the sequence. A single nucleotide substitution mutation is the most common, as most large-scale nucleotide swaps involve other mechanisms.

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Sickle-Cell Anemia
The blood disease Sickle-cell anemia is caused by a point mutation which codes for a unit of hemoglobin. Hemoglobin is a multi-protein complex, responsible for carrying oxygen and supporting the shape of blood cells. The substitution mutation causes a glutamic acid in the protein to be changed to a valine amino acid.
Healthy cell and Sickle cell anemia are different. For the normal red blood cell, it is instructed for blood flow. For the sickle red blood cell, these damaged red blood cells (sickle cells) clump together. They can't move easily through the blood vessels, they get stuck in small vessels and block blood flow. This blockage stops the movement of healthy oxygen-rich blood.

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The effects to autosome and sex chromosome

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The effects to autosome and sex chromosome

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Impacts on Offspring
There are two major types of cells in the body: body cells and germ cells. Mutations happen in both of these cell types, but only mutation in germ cells may be passed from parent to offspring. Mutation in germ line affect the phenotype of offspring.

- Germ cell: involved in the formation of gametes that reproduces sexually.
Mutation in germ line affect the phenotype of offspring. Often, this effect is so harmful that offspring do not develop properly or die before they can reproduce.

- Body cell= Somatic cell: include all other cells of the body except sperm and egg cells. These alterations can (but do not always) cause cancer or other diseases. They are not carried to the offspring.

Germline mutations occur in gametes. These mutations are especially significant because they can be transmitted to offspring and every cell in the offspring will have the mutation.

Mutations in somatic cells are called somatic mutations. Because they do not occur in cells that give rise to gametes, the mutation is not passed along to the next generation by sexual means. To maintain this mutation, the individual containing the mutation must be cloned.

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-Caused by insertion or deletion in a DNA sequence.

- Drastically alters the protein

Insertion and Deletion
-Insertion referes to the insertion of a nucleotide pair at some location on the DNA molecule. A deletion is the removal of a nucleootide pair at some posistion on the DNA.

-An Insertion or Deletion may or may not cause a shift in the reading frame

-Reading frame  is the sequence of codons that is read by the ribosome during polypeptide synthesis.

Insertion that causes a shift of the reading frame
-GCG AGC TAG as the nucleotide sequence

-When its actually transcribe the molecule, RNA polymerase reads from 3' to 5'

-Use the mRNA molecule to translate it into the amino acid sequence

-once the mRNA molecule is synthesizes, it will use the mRNA molecule and the ribosomes which are going to translate the code to the amino acid sequence

-Ribosome will use the genetic code which consists of 64 codons

-The insertion of the cytosine nucleotide between the 7th and 8th DNA nucleotide causes a shift in the mRNA reading frame.

-polypeptide aminoacid sequence

-Changes the codons that are read by the ribosome and changes the sequence of amino acidsin the polypeptide chain.

-Leads to a non functional protein.

-Any insertion, or deletion that is not a multiple of three nucleotides will cause a frameshift mutation.

What happens when theres three nucleotide sequence is inserted.

-Insert three nucleotides the CAG nucleotide between 6th and 7th nucleotide.

-Translated code

-When Ribosome and genetic code is used to translate the mutated mRNA strand, you can see the following result.(Leucine-Leucine - Alanine - Arginin)

-It does not lead to a frame shift mutation.

-Such mutations are called non-frameshift mutations because all the amino acid will be produced.