What type of mutation occurs when a single base in a DNA sequence is replaced by another base?
Base substitution
May or may not change the amino acid due to degeneracy of the genetic code.
What type of mutation occurs when one or more bases are removed from a DNA sequence?
Base deletion
Often causes a frameshift, altering many downstream amino acids.
Changes in the sequence of bases within a gene are known as what type of mutations?
Gene mutations
These alter the DNA base sequence within a gene.
True or False:
All base substitutions change the amino acid sequence of a protein.
False
Because the genetic code is degenerate, different codons can code for the same amino acid.
What type of agents increase the rate at which mutations occur in DNA?
Mutagenic agents
Examples include radiation and some chemicals.
What failure of chromosomes during meiosis can lead to cells with abnormal chromosome numbers?
Non-disjunction
Occurs when chromosomes fail to separate properly during meiosis, leading to gametes with too many or too few chromosomes. This can result in conditions such as Down syndrome (trisomy 21).
True or False:
Meiosis produces daughter cells that are genetically identical to each other.
False
Genetic variation arises during meiosis.
How many haploid daughter cells are usually produced from one diploid cell after meiosis?
Four
Meiosis involves two successive nuclear divisions.
What term describes the separation of homologous chromosome pairs into different daughter cells during meiosis?
Independent segregation
Each pair separates independently, generating variation.
What process occurs when homologous chromosomes exchange segments of DNA during meiosis?
Crossing over
Occurs during prophase I and increases genetic variation.
True or False:
Crossing over occurs between homologous chromosomes during meiosis.
True
This exchange of genetic material produces new allele combinations.
What term describes the fusion of two haploid gametes to form a diploid zygote?
Fertilisation
Increases genetic variation because gamete combinations are random.
What phrase describes the pairing of gametes during reproduction that produces many possible allele combinations?
Random fertilisation
Any sperm can fuse with any egg, increasing variation.
Fill in the blank:
Without crossing over, the number of possible chromosome combinations produced by meiosis is calculated using the expression ______ where n is the number of homologous chromosome pairs.
2n
Represents the number of combinations from independent segregation.
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2: Biological Molecules119
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2: Water & Inorganic Ions19
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2: Cells52
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2: Cell Division20
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2: Membranes & Transport20
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