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Summary BIOL 1107 TEST 4 STUDY GUIDE
- Course
- BIOL 1107
- Institution
- University Of Georgia
Detailed study guide for 4th bio test. Includes all material needed for the fourth test and tophat questions as well as diagrams needed
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TRAIT INHERITANCE● Define homologous chromosomes, alleles, and ploidy (haploid, diploid, or
polyploid).
○ Homologous chromosomes: chromosomes that are the same size, have
the same genes, and pair during meiosis
○ Alleles: different version of the same gene
○ Ploidy: how many sets of chromosomes in the nucleus
■ Haploid: single chromosome set (n)
■ Diploid: two chromosome sets (2n)
■ Polyploid: greater than two sets of chromosomes (3n, 4n, 5n, 6n)
● Compare meiosis with mitosis in terms of the major events that occur and
outcomes.
○ Meiosis: more complex, division of nucleus into 4 nuclei that contain half
the number of chromosomes and are not identical to each other.
○ Cytokinesis has to happen twice
○ DNA replication is the same for meiosis as mitosis.
○ Meiosis 1: chromosomes condense, spindle forms, nuclear envelope
disappears. Homologous chromosomes pair up. Tetrads are UNIQUE to
meiosis. Crossing over appears.
○ Meiosis 2: identical to mitosis. Does not cause a change in chromosomes.
● Discuss how genetic diversity is produced through meiosis and sexual
reproduction.
○ Offspring is produced by sexual reproduction and are genetically different
from both parents and also from each other.
○ This is from:
■ Independent assortment: assignment of tetrads during metaphase
of meiosis I is independent and random.
■ Fertilization: the fusion of gametes. Produces an incredible amount
of genetic diversity.
■ Crossing over: produces new combinations of alleles in the
chromosomes that are distinct from either parents. Unlimited variety
of gametes and offspring.
● Explain why saying “I’m a quarter Irish!” is most likely inaccurate based on
meiosis
○ Due to independent assortment, fertilization, and crossing over you will
never exactly inherit “25%” of your grandparents.
Top Hat Question
The HBA gene is found on chromosome 16 and encodes the alpha chain of
hemoglobin. During our evolutionary past, this gene was duplicated to form HBA1 and
HBA2. How many copies of the HBA gene do human somatic cells contain?
(A) 1
, (B) 2
(C) 4
(D) 8
Top Hat Question
During meiosis, when do cells first contain half the number of chromosomes as the
parent cell?
(A) Middle of meiosis I
(B) End of meiosis I
(C) Middle of meiosis II
(D) End of meiosis II
MEIOSIS
● Define nondisjunction and provide examples.
○ An error that happens during meiosis where chromosomes are incorrectly
distributed to the daughter nuclei.
○ Can end up with too many or too little
○ Caused by spindle not pulling apart the chromosomes correctly.
○ Having the wrong number of chromosomes is usually not survivable.
○ Sex chromosomes are usually more forgiving than autosomal
chromosomes.
○ Examples of nondisjunction are
■ Trisomy 21(down’s syndrome)
● The only autosomal chromosome were you can have three
and survive
■ Klienfelter’s syndrome (only in males)
● Three sex chromosomes
● Describe how meiosis is different in male and female mammals and
discuss the implications.
○ Gametogenesis
○ Eggs and sperm have different meiosis.
○ For eggs: the eggs are already present before birth. Begin meiosis before
birth but stops after meiosis I until puberty. One or a few eggs start up
meiosis until meiosis II, it stops to wait to be fertilized. Never finishes
unless it is fertilized. Much larger than sperm. POLAR BODY DOES
NOTHING. Higher error rate in eggs.
○ For sperm: begins at puberty and is continuous for life. Takes about two
months. Sperm is much younger than eggs.
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