Transcript Chromosomes and Mutations Chromosomes and

Chromosomes,
Genes, and
Mutations
What are chromosomes?
• Chromosomes are packages of tightly-coiled
(condensed) DNA
• Each chromosome is tightly coiled around proteins called
histones
What are chromosomes?
Each human has 23 sets (pairs) of chromosomes, or 46
total chromosomes
What are genes?
• A molecular unit of heredity
• The name for sections of DNA (and therefore RNA) that
code for a specific protein (which has a specific function
in the organism)
What are genes?
Since genes are
bands/sections of
DNA, that means
genes are also
bands/sections of
chromosomes
How are genes inherited?
• Each person has two copies of each gene – one on each
chromosome
• You inherit one chromosome from your mom, and one
chromosome from your dad
How are genes mutated?
• Genes can be mutated when the DNA is mutated or
when the chromosomes are mutated
• There are two types of DNA (gene) mutations:
• Point Mutations: a change in a single base pair
• Frameshift Mutations: a single base is added or deleted
from DNA
• Chromosomes can be mutated as well (long segments of
DNA)…
What are examples of
chromosomal mutations?
• Deletions: part of the chromosome is left out
What are examples of
chromosomal mutations?
• Inversions: part breaks out and reinserts itself backwards
What are examples of
chromosomal mutations?
• Translocations: part breaks off and is added into a
different chromosome
What are examples of
chromosomal mutations?
• Non-Disjunction: failure of homologous chromosomes to
separate properly during meiosis
What causes chromosomal
mutations?
• Problems that occur during meiosis
What causes chromosomal
mutations?
• Environmental agents (x-rays, UV light, radioactivity)
What are the results of
chromosomal mutations?
• If it occurs in gametes (sex) cells:
• Can cause birth defects, miscarriage, or no change
• Few are passed on to next generation because zygote
usually dies
• If it occurs in somatic (body) cells:
• Can lead to cancer
• Can have no change