#14: Polyploidy and Organellar Genetics

What term describes cells that contain complete sets of chromosomes?
A) Aneuploid
B) Euploid
C) Monosomic
D) Trisomic

Euploid

Which of the following is an example of aneuploidy?
A) Having 23 pairs of chromosomes
B) Having 22 pairs of chromosomes and one extra chromosome 21
C) Having two copies of each chromosome
D) None of the above

Having 22 pairs of chromosomes and one extra chromosome 21

What is monosomy?
A) Having three copies of a chromosome
B) Missing one chromosome from a pair
C) Having one complete set of chromosomes
D) None of the above

Missing one chromosome from a pair

When a cell has an extra chromosome, it is called ________.

trisomy

T/F: Aneuploidy refers to a cell having either missing or extra chromosomes rather than complete pairs.

true

Which trisomy is associated with Patau syndrome?
A) Trisomy 13
B) Trisomy 18
C) Trisomy 21
D) Trisomy 22

Trisomy 13

Most autosomal trisomies are lethal except for chromosomes:
A) 13, 18, and 21
B) 21, 22, and X
C) 13, 14, and 15
D) 16, 18, and 20

13, 18, and 21

The presence of an extra chromosome in autosomes typically results in:
A) No effect
B) Only physical changes
C) Intellectual and developmental disabilities
D) Only intellectual disabilities

Intellectual and developmental disabilities

Trisomy 18 is also known as ________ syndrome.

Edwards

Most autosomal aneuploidies are ________, meaning the embryo usually does not survive.

lethal

Trisomy 13 leads to ________ syndrome.

Patau

T/F: Extra copies of chromosomes can disrupt normal development and cause specific physical features.

true

Turner syndrome is characterized by which of the following karyotypes?
A) XXY
B) XO
C) XXX
D) XYY

XO

Which syndrome results from an extra X chromosome in males?
A) Turner syndrome
B) Klinefelter syndrome
C) Down syndrome
D) Edwards syndrome

Klinefelter syndrome

A person with Turner syndrome is typically:
A) Male and sterile
B) Female and sterile
C) Male and fertile
D) Female and fertile

Female and sterile

Symptoms of Klinefelter syndrome include:
A) Short stature and infertility
B) Tall stature and infertility
C) Tall stature and increased fertility
D) Short stature and increased fertility

Tall stature and infertility

Turner syndrome is caused by having only one ______ chromosome.

X

Klinefelter syndrome occurs when a male has an extra ______ chromosome.

X

Both Turner and Klinefelter syndromes can cause ______ (inability to have children).

sterility

T/F: Aneuploidy of sex chromosomes often results in less severe symptoms compared to autosomal aneuploidy.

true

T/F: Individuals with Turner syndrome are typically taller than average.

false

T/F: Klinefelter syndrome is caused by having two Y chromosomes.

false

What process helps balance gene expression in cells with more than one X chromosome?
A) Gene duplication
B) X inactivation
C) Crossing over
D) DNA methylation

X inactivation

Why does having an extra X chromosome (as in XXY) not always cause severe symptoms?
A) Because the extra X chromosome is completely deleted
B) Because one X chromosome is usually inactivated
C) Because Y chromosome compensates for X chromosome genes
D) Because the extra chromosome is always lost during cell division

Because one X chromosome is usually inactivated

Which gene on the X chromosome escapes inactivation and affects skeletal development?
A) SHOX
B) SRY
C) BRCA1
D) DMD

SHOX

Abnormal copies of SHOX gene can cause which of the following?
A) Color blindness
B) Skeletal abnormalities such as short or tall stature
C) Increased cognitive abilities
D) Increased fertility

Skeletal abnormalities such as short or tall stature

In females, one X chromosome is usually ______ to balance gene expression.

inactivated

Some genes, like the ______ gene, remain active even on the inactivated X chromosome.

SHOX

Changes in the number of active copies of SHOX gene can lead to ______ problems, including short or tall stature.

skeletal

T/F: The SHOX gene is completely inactivated along with the rest of the X chromosome in cells with multiple Xs.

false

T/F: X inactivation helps explain why Klinefelter syndrome (XXY) symptoms are often less severe than autosomal trisomies.

false

What is the cause of aneuploidy during meiosis?
A) Crossing over
B) DNA replication errors
C) Nondisjunction
D) Gene mutation

Nondisjunction

During which stage does nondisjunction result in homologous chromosomes failing to separate?
A) Meiosis I
B) Meiosis II
C) Mitosis
D) DNA replication

Meiosis I

Nondisjunction during meiosis II results in:
A) Both homologous chromosomes going to the same cell
B) Both sister chromatids going to the same gamete
C) Normal chromosome separation
D) None of the above

Both sister chromatids going to the same gamete

Meiotic nondisjunction is the failure of ______ to separate during meiosis I or meiosis II.

homologous chromosomes (meiosis I) / sister chromatids (meiosis II)

If nondisjunction happens in meiosis I, ______ chromosomes move into the same daughter cell.

homologous

Nondisjunction in meiosis II causes ______ chromatids to move into the same gamete.

sister

Why does the risk of Down Syndrome increase with the mother's age?
A) Older mothers have more chromosomes
B) Eggs complete meiosis immediately after birth
C) Eggs remain arrested in meiosis for many years, increasing chance of errors
D) Older mothers have more exposure to radiation

Eggs remain arrested in meiosis for many years, increasing chance of errors

At which stage of meiosis do the two copies of chromosome 21 normally separate in egg cells?
A) Meiosis II
B) Meiosis I
C) Mitosis
D) Fertilization

Meiosis I

What happens when the two copies of chromosome 21 fail to separate during meiosis?
A) The egg has no chromosome 21
B) The egg has one copy of chromosome 21
C) The egg has two copies of chromosome 21
D) The egg has three copies of chromosome 21

The egg has two copies of chromosome 21

The increased risk of nondisjunction with maternal age is because egg cells start meiosis before birth but complete it only during ______.

ovulation (or when the egg is released)

Poor or no ______ on chromosome 21 can increase the risk of nondisjunction.

recombination

T/F: The longer the egg stays arrested in meiosis, the higher the chance of nondisjunction errors.

true

T/F: Nondisjunction usually happens during meiosis II in the case of Down Syndrome.

false (usually meiosis I)

T/F: More recombination on chromosome 21 increases the risk of nondisjunction.

false (less or no recombination increases the risk)

T/F: A fertilized egg with trisomy 21 has three copies of chromosome 21, causing Down Syndrome.

true

T/F: If recombination between homologous chromosomes on chromosome 21 is reduced or absent, nondisjunction is more likely to occur.

true

T/F: less mixing (recombination) = more errors = higher chance of nondisjunction

true

During meiosis in individuals with Down syndrome, what does trivalent formation refer to?
A) Three homologous chromosomes fail to pair and segregate independently
B) All three copies of chromosome 21 pair up together forming a group of three chromosomes
C) Two chromosomes pair and the third is lost
D) Chromosomes fail to undergo recombination

All three copies of chromosome 21 pair up together forming a group of three chromosomes

Which of the following is true about univalent formation in trisomy 21 meiosis?
A) All three chromosomes pair normally
B) Two chromosomes pair while the third remains unpaired
C) All three chromosomes fail to separate
D) Univalent formation guarantees balanced gametes

Two chromosomes pair while the third remains unpaired

In individuals with Down syndrome, the unusual chromosome pairing during meiosis can lead to formation of a ______ or a ______.

trivalent; univalent

Unbalanced gametes are produced when chromosomes separate ______ during meiosis in trisomic individuals.

incorrectly

T/F: Individuals with Down syndrome cannot have healthy children due to their trisomy.

false

T/F: Some gametes produced by individuals with trisomy 21 can contain the correct number of chromosomes despite abnormal segregation.

true

In a hexaploid wheat organism with 42 chromosomes, what is the value of x (the number of chromosomes in a single complete set)?
A) 21
B) 7
C) 42
D) 14

7

For a diploid organism with 46 chromosomes, the haploid number (n) is:
A) 46
B) 92
C) 23
D) 69

23

The symbol n represents the number of chromosomes in a _______ cell, while x represents the number of chromosomes in a single, complete _______.

gamete; set

T/F: In a hexaploid organism, n is always equal to x.

false

Why are monoploid plants useful for identifying genes important for fitness?
A) They have multiple copies of each gene, making mutations less visible
B) They have only one copy of each chromosome, so mutations show clear effects
C) They reproduce very quickly
D) They have enhanced resistance to all diseases

They have only one copy of each chromosome, so mutations show clear effects

What chemical is commonly used to convert sterile monoploid plants into fertile diploids?
A) Auxin
B) Gibberellin
C) Colchicine
D) Ethylene

Colchicine

Monoploid plants have _______ copies of each chromosome, making it easier to detect effects of mutations.

one

Scientists grow monoploid plants from _______ cells and then use plant hormones and nutrients to grow full plants.

pollen

T/F: Monoploid plants are usually fertile because they have complete chromosome pairs.

false

T/F: Doubling the chromosome number in monoploid plants using colchicine produces diploid plants that are fertile and genetically stable.

true

why are monoploid plants generally sterile?

They don’t have chromosome pairs, which are needed for proper separation during reproduction  

How does colchicine cause chromosome doubling in plants?
A) It speeds up DNA replication
B) It prevents spindle fiber formation, blocking chromosome separation
C) It increases the number of chromosomes by mutation
D) It promotes faster cell division

It prevents spindle fiber formation, blocking chromosome separation

What is the immediate result when colchicine blocks spindle fiber formation during cell division?
A) Cell division proceeds normally
B) Two daughter cells with half the chromosome number are produced
C) The cell does not split and ends up with double the chromosome number
D) Chromosomes are degraded

The cell does not split and ends up with double the chromosome number

Colchicine blocks ______ fiber formation, preventing the separation of chromosomes during cell division.

spindle

When colchicine-treated cells fail to divide, they retain _______ times the original number of chromosomes.

two

T/F: Colchicine treatment in developing meiocytes allows formerly sterile monoploid plants to reproduce sexually.

true

T/F: Colchicine promotes the degradation of chromosomes, leading to sterility in plants.

false

Polyploidy refers to an organism having:
a) Exactly two sets of chromosomes
b) More than two sets of chromosomes
c) Missing chromosomes
d) One set of chromosomes

More than two sets of chromosomes

Which of the following is a common outcome when a cell fails to divide properly during mitosis?
a) Formation of haploid cells
b) Formation of one big cell with duplicated chromosome sets
c) Loss of all chromosomes
d) Production of abnormal gametes with no chromosomes

Formation of one big cell with duplicated chromosome sets

Autopolyploidy occurs when:
a) Chromosome sets come from two different species
b) Chromosome sets come from the same species
c) The organism loses chromosomes
d) There is a deletion in the chromosome set

Chromosome sets come from the same species

Polyploid plants often have:
a) Smaller fruit and seeds than diploids
b) Larger fruit, seeds, or leaves than diploids
c) No fruit or seeds at all
d) Identical growth to diploids

Larger fruit, seeds, or leaves than diploids

A tetraploid plant has __________ sets of chromosomes.

4

If two diploid gametes fuse during fertilization, the resulting plant is ____________.

tetraploid

___________ is a type of polyploidy where all chromosome sets come from the same species.

Autopolyploidy

T/F: Polyploidy occurs only during meiosis errors.

false (mitosis meiosis)

What is the primary goal of creating an allopolyploid by crossing two related plant species?
a) To reduce the number of chromosomes
b) To study meiosis in animals
c) To combine beneficial traits from both parent species
d) To eliminate protein production in crops

To combine beneficial traits from both parent species

When wheat and rye are crossed, the F1 hybrid is sterile because:
a) It has too few chromosomes
b) Its chromosomes are all identical
c) The chromosomes cannot pair properly during meiosis
d) The DNA is completely incompatible

The chromosomes cannot pair properly during meiosis (cannot be equally separated)

What process is used to restore fertility to a sterile hybrid plant?
a) Radiation
b) Pollination
c) Cold shock
d) Chromosome doubling using colchicine

Chromosome doubling using colchicine

Which of the following statements about allopolyploids is correct?
a) They contain one set of chromosomes total
b) They always occur naturally in animals
c) They are formed by crossing two unrelated species
d) They contain complete sets of chromosomes from two different species

They contain complete sets of chromosomes from two different species

An _____________ is a plant that contains a full set of chromosomes from each of two different but related species.

allopolyploid

One benefit of crossing wheat and rye is to combine high protein from wheat with high __________ content from rye.

lysine

T/F: The F1 generation of a wheat-rye cross is sterile because it has 21 single chromosomes that cannot pair properly.

true

T/F: Colchicine promotes chromosome pairing by preventing cell division and doubling the chromosome number.

true

Which structure in plant cells contains its own DNA and is responsible for capturing sunlight?
a) Nucleus
b) Mitochondria
c) Ribosome
d) Chloroplast

Chloroplast

What pigment is found in thylakoids that helps capture light energy?
a) Hemoglobin
b) Melanin
c) Chlorophyll
d) Keratin

Chlorophyll

What is the main role of chloroplast DNA?
a) Regulate mitosis in animal cells
b) Code for photosynthetic proteins within the chloroplast
c) Store long-term memory
d) Transport oxygen in cells

Code for photosynthetic proteins within the chloroplast

Chloroplasts are ___________ bound organelles found in the cytoplasm of plant cells.

membrane

In corn, each leaf cell can have up to ___________ chloroplasts.

50

The internal structures of chloroplasts that contain chlorophyll are called ____________.

thylakoids

T/F: Chloroplasts can perform photosynthesis because they contain chlorophyll and their own DNA.

true

What is the typical structure of chloroplast DNA in plants?
a) Linear
b) Circular
c) Helical
d) Branched

Circular

How many genes are typically encoded by the chloroplast genome?
a) 30–50
b) 70–90
c) ~120
d) Over 500

~120

hich of the following functions are supported by genes in the chloroplast genome?
a) DNA repair and apoptosis
b) Photosynthesis and translation
c) Glycolysis and protein folding
d) Cell division and hormone regulation

Photosynthesis and translation

How many copies of chloroplast DNA are typically present per chloroplast?
a) 1–2
b) 5–10
c) 15–20
d) 50–100

15–20

T/F: Chloroplast DNA is highly compact and has very little non-coding space.

true

In most plant species, chloroplast DNA is inherited from:
a) The father
b) Both parents equally
c) The mother
d) It varies randomly

The mother