Free WACE Biology Flashcard Review
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How does binary fission maintain continuity in a bacterial lineage?
The chromosome replicates, copies segregate as the cell elongates, and division produces two cells that normally inherit the same genome apart from mutation.
What is the genetic outcome of mitosis after DNA replication?
Two daughter nuclei with the same chromosome complement and usually the same DNA sequence as the parent nucleus.
What separates in anaphase I of meiosis?
Homologous chromosome pairs separate; sister chromatids remain joined at their centromeres.
What separates in anaphase II of meiosis?
Sister chromatids separate and move to opposite poles.
Why does meiosis halve chromosome number?
One DNA replication is followed by two divisions, with homologous chromosomes separated before sister chromatids.
A species has 2n = 12. How many chromosomes should each normal gamete contain?
Six. Gametes are haploid, so n = 12/2 = 6.
Why does fertilisation restore diploid chromosome number?
Two haploid gametes fuse, combining one chromosome set from each parent.
How do mitosis and meiosis differ in genetic purpose?
Mitosis preserves chromosome complement for growth or replacement; meiosis produces varied haploid gametes for sexual reproduction.
Why are four products of animal meiosis not four predetermined offspring?
Each functional gamete still needs fertilisation. Not every meiotic product becomes a functional gamete: animal oogenesis also produces polar bodies. Random gamete fusion adds variation.
Correct the claim that cytokinesis copies DNA.
DNA is copied during S phase. Cytokinesis divides cytoplasm after nuclear chromosome separation.
What are the three components of a DNA nucleotide?
Deoxyribose sugar, a phosphate group and one nitrogenous base.
Which bases pair in double-stranded DNA?
Adenine pairs with thymine, and cytosine pairs with guanine.
What does antiparallel mean for DNA strands?
Their sugar–phosphate backbones run in opposite directions: one 5′ to 3′ and the other 3′ to 5′.
Why can one DNA strand template a complementary strand?
Specific base pairing determines which nucleotide is added opposite each exposed base.
What makes DNA replication semi-conservative?
Each daughter DNA molecule contains one parental strand and one newly synthesised strand.
After S phase, does chromosome number double?
No. DNA amount and chromatid number double, but chromosome number counted by centromeres stays the same.
A double-stranded DNA molecule contains 28% adenine. What percentage is cytosine?
A pairs with T, so A+T = 56%. The remaining 44% is C+G, giving 22% cytosine.
Why is DNA polymerase proofreading important?
It removes many mismatched nucleotides, increasing replication fidelity while not eliminating all mutations.
Where is most eukaryotic nuclear DNA organised?
In linear chromosomes associated with proteins inside the nucleus; organelles can also contain small DNA genomes.
Correct the claim that hydrogen bonds form the DNA backbone.
Covalent sugar–phosphate bonds form each backbone; hydrogen bonds join complementary bases between strands.