3C1 Heredity Flashcards

Explain how structure, function, and processes of DNA and RNA underlie genetic inheritance and variation. (81 cards)

1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

DNA is a molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known living organisms.

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2
Q

What does RNA stand for?

A

Ribonucleic acid

RNA plays a role in protein synthesis and can act as genetic material in some viruses.

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3
Q

What is the shape of the DNA molecule?

A

Double helix

DNA’s double-helix structure was discovered by James Watson and Francis Crick, supported by Rosalind Franklin’s X-ray diffraction data.

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4
Q

What sugar is found in DNA?

A

Deoxyribose

Deoxyribose is a 5-carbon sugar that lacks an oxygen atom at the 2’ position, distinguishing it from ribose in RNA.

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5
Q

Which base is unique to RNA?

A

Uracil

Uracil replaces thymine in RNA and pairs with adenine during base pairing.

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6
Q

True or False:

Thymine is found in RNA.

A

False

Thymine is found only in DNA, whereas RNA contains uracil instead.

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7
Q

What are the four nitrogenous bases in DNA?

A
  • Adenine
  • Thymine
  • Cytosine
  • Guanine

Adenine pairs with thymine, and cytosine pairs with guanine through complementary base pairing.

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8
Q

What are the building blocks of DNA?

A

Nucleotides

Each nucleotide consists of a phosphate group, deoxyribose sugar, and a nitrogenous base.

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9
Q

Fill in the blank:

In DNA, adenine pairs with _______.

A

Thymine

Adenine pairs with thymine through two hydrogen bonds, maintaining the double-helix structure.

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10
Q

What is the function of DNA?

A

Storing genetic information.

DNA serves as the blueprint for all cellular processes and is passed from parent to offspring.

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11
Q

True or False:

RNA is double-stranded like DNA.

A

False

RNA is typically single-stranded, although it can fold into complex shapes for specific functions.

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12
Q

Fill in the blank:

DNA replication occurs in the ________ of eukaryotic cells.

A

nucleus

DNA replication takes place during the S-phase of the cell cycle in the nucleus.

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13
Q

What is transcription?

A

The process of creating RNA from a DNA template.

This occurs in the nucleus where RNA polymerase synthesizes messenger RNA (mRNA).

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14
Q

What are the three types of RNA?

A
  • mRNA
  • tRNA
  • rRNA

mRNA carries genetic code, tRNA brings amino acids, and rRNA forms ribosomes.

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15
Q

What is the function of mRNA?

A

It carries the genetic code for protein synthesis.

Messenger RNA (mRNA) transfers genetic information from DNA to ribosomes for translation.

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16
Q

Where does transcription occur in eukaryotic cells?

A

In the nucleus.

In eukaryotes, DNA is located in the nucleus, so transcription must occur there.

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17
Q

What enzyme catalyzes transcription?

A

RNA polymerase

This enzyme binds to the DNA template strand and synthesizes complementary RNA.

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18
Q

True or False:

Transcription occurs in the cytoplasm of prokaryotes.

A

True

In prokaryotes, transcription occurs in the cytoplasm because they lack a nucleus.

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19
Q

What are the three main stages of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination

Initiation begins the process, elongation builds the RNA strand, and termination ends transcription.

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20
Q

Fill in the blank:

RNA polymerase binds to the _______ during transcription initiation.

A

promoter

The promoter is a DNA sequence that signals the start of transcription.

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21
Q

What is the central dogma of molecular biology?

A

DNA → RNA → Protein

The central dogma explains the flow of genetic information: DNA is transcribed into RNA, which is then translated into proteins.

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22
Q

Why is the central dogma important?

A

It explains how genetic information leads to protein synthesis.

The central dogma outlines the essential flow of information needed for gene expression and protein production.

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23
Q

Fill in the blank:

During translation, amino acids are brought to the ribosome by _______.

A

tRNA

(transfer RNA)

tRNA contains anticodons that pair with mRNA codons, allowing amino acids to assemble into proteins.

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24
Q

Define:

codon

A

A sequence of 3 nucleotides that code for a specific amino acid.

Also referred to as triplet code, these sequences exist in both DNA and RNA.

For example, the codon “CAG” codes for the synthesis of the amino acid glutamine.

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25
What is the start codon in **mRNA**?
AUG ## Footnote **AUG** codes for the amino acid methionine, and signals the beginning of translation.
26
What **molecule** provides energy for translation?
GTP | (Guanosine triphosphate) ## Footnote **GTP** provides energy for various steps in the translation process, such as tRNA binding and ribosome movement.
27
What are **chromosomes**?
**Structures** made of DNA and proteins that carry genetic information. ## Footnote Chromosomes are found in the nucleus of eukaryotic cells and contain **genes** that determine traits.
28
What is a **karyotype**?
A **visual representation** of all the chromosomes in a cell. ## Footnote They are used to *study* chromosome structure, number, and abnormalities.
29
# Define: Gene
A **segment of DNA** that codes for a specific protein or trait. ## Footnote They are the basic units of heredity and determine specific characteristics, such as eye color or blood type.
30
Where are genes **located**?
On chromosomes. ## Footnote Genes occupy specific positions called **loci** on chromosomes. Each gene carries instructions for a trait.
31
# Fill in the blank: Chromosomes are **made** up of \_\_\_\_\_ and proteins.
DNA ## Footnote Chromosomes consist of tightly packed DNA molecules wrapped around proteins called histones.
32
How **many** chromosomes do humans have in each somatic cell?
46 chromosomes (23 pairs) ## Footnote Humans inherit 23 chromosomes from *each parent*, resulting in 23 pairs of homologous chromosomes.
33
What are **autosomes**?
Chromosomes that **do not** determine sex. ## Footnote Humans have *22 pairs* of autosomes, which carry genes for most traits.
34
What are **sex chromosomes**?
Chromosomes that **determine the biological sex** of an organism. ## Footnote Humans have **two** sex chromosomes—XX in females and XY in males. There are some genetic conditions where people inherit more than two sex chromosomes, such as Klinfelter (XXY) and Triple X Syndrome (XXX).
35
What genetic disorder is characterized by an extra copy of **Chromosome 21**?
Down Syndrome ## Footnote Down syndrome, or *trisomy 21*, occurs when there is a third copy of chromosome 21 instead of the usual two, leading to developmental and intellectual disabilities.
36
# Fill in the blank: \_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ is a chromosomal **abnormality** characterized by an extra chromosome 13.
Patau syndrome ## Footnote *Patau syndrome* (trisomy 13) leads to severe intellectual disability, physical abnormalities, and a shortened life expectancy.
37
What are **chromosomal** mutations?
**Changes** in the structure or number of chromosomes. ## Footnote Chromosomal mutations can include deletions, duplications, inversions, and translocations. They can lead to disorders such as Down syndrome or Turner syndrome.
38
# True or False: All chromosomes are **identical** in structure and function.
False ## Footnote Chromosomes vary in size, shape, and the genetic information they carry. Autosomes and sex chromosomes have different roles.
39
What is an **allele**?
A **variant** form of a gene. ## Footnote Alleles are *different versions* of the same gene that can result in variations in a trait, such as blue or brown eyes.
40
Generally, how **many** alleles for a gene does an individual inherit?
**Two**—one from each parent. ## Footnote For *most* traits, individuals inherit one allele from the mother and one from the father.
41
What is a **sex-linked** trait?
A trait controlled by **genes located on the X or Y chromosome**. ## Footnote Sex-linked traits are often more **common** in males because they have only one X chromosome. An example is red-green color blindness, which is X-linked.
42
Why are sex-linked traits more common in **males** than in females?
Males have only **one** X chromosome. ## Footnote Males inherit their X chromosome from their mother and the Y chromosome from their father. A recessive allele on the X chromosome will be expressed in males because they lack a second X chromosome to mask it.
43
List **three advantages** of sexual reproduction.
1. Genetic Variation 2. Better Disease Resistance 3. Elimination of Harmful Mutations ## Footnote **Genetic Variation** – Increases adaptability and evolution potential. **Better Disease Resistance** – Inheriting diverse genes may improve survival. **Elimination of Harmful Mutations** – Genetic recombination can help remove deleterious traits.
44
List **three disadvantages** of sexual reproduction.
1. Requires finding a mate. 2. Slower reproductive cycle. 3. High energy investment in offspring. ## Footnote Mating can be **difficult**, especially in isolated populations. The process is time-consuming, and energy is spent on producing and nurturing offspring, making it less efficient in rapid population expansion.
45
What makes **asexual reproduction** efficient?
It allows **rapid** population growth. ## Footnote Since offspring are *clones* of the parent, no time is wasted on finding a mate. This is beneficial in environments where survival depends on quickly increasing numbers.
46
List **three types** of asexual reproduction.
1. Binary fission 2. Budding 3. Fragmentation ## Footnote **Binary fission** – Cell splits into two (e.g., bacteria). **Budding** – Offspring grows from the parent (e.g., yeast, hydra). **Fragmentation** – Body parts regenerate into new organisms (e.g., starfish).
47
# True or False: Sexual reproduction results in **faster population growth** than asexual reproduction.
False ## Footnote *Sexual reproduction* requires finding a mate and has a longer reproductive cycle, whereas *asexual reproduction* allows for rapid cloning and exponential growth.
48
# Fill in the blank: Sexual reproduction **increases** ____ ____ within a population.
genetic variation ## Footnote This variation helps species **survive** environmental changes, as some individuals may have traits that offer a *survival advantage*.
49
What does a **Punnett square** show?
It shows the **probability** of offspring genotypes. ## Footnote Punnett squares help *visualize* how alleles from both parents combine, providing a probability of different genotype combinations in the offspring.
50
# Define: homozygous genotype
Having **two identical alleles** for a gene. ## Footnote A homozygous genotype can be **either** dominant (AA) or recessive (aa).
51
What is **genotype**?
The genetic **makeup** of an organism. ## Footnote Genotype refers to the *combination* of alleles (e.g., AA, Aa, or aa) inherited from both parents that determine an organism's traits.
52
# Define: phenotype
The **outward presentation** of an individual based on the genotype. ## Footnote Phenotypes can be easily observed, such as eye color. Phenotypes are determined by the genotype, or genetic allele combination, of someone's DNA.
53
What is a **dominant** trait?
A trait where **only 1 copy of the allele is needed** to express the trait. ## Footnote Dominant traits are expressed in both homozygous dominant (AA) and heterozygous (Aa) individuals, masking the recessive trait.
54
What is a **recessive** trait?
A trait expressed only when **both alleles are recessive**. ## Footnote A recessive trait will not be observed in the presence of a dominant allele (Aa or AA) but will be expressed in homozygous recessive individuals (aa).
55
What is the **genotype** of an individual with a recessive trait?
Homozygous recessive (aa) ## Footnote A recessive trait can only be observed when both alleles are recessive, meaning the genotype must be **aa**.
56
What is the **genotype** of a homozygous dominant individual?
AA ## Footnote Homozygous dominant individuals have two copies of the dominant allele, ensuring the dominant trait is expressed.
57
# Define: heterozygous genotype
Having **two different alleles** for a gene.
58
# True or False: Heterozygous individuals express the **recessive** trait.
False ## Footnote Heterozygous individuals (Aa) express the **dominant** trait, as the dominant allele masks the recessive allele.
59
# Fill in the blank: The complete **set** of an organism's genetic material is called its \_\_\_\_\_\_\_\_.
genome ## Footnote The **genome** includes all the DNA in an organism, including all its genes and chromosomes.
60
What is the **result** of a homozygous dominant x homozygous recessive cross?
All offspring will be **heterozygous**. ## Footnote A cross between homozygous dominant (AA) and homozygous recessive (aa) parents produces offspring with the genotype **Aa**, all expressing the dominant trait.
61
# True or False: Two homozygous recessive parents can produce offspring with a **dominant** trait.
False ## Footnote Two homozygous recessive parents (aa x aa) can only pass on **recessive** alleles, so all offspring will express the recessive trait.
62
What is the **probability** of offspring having a dominant phenotype in a cross between a heterozygous (Aa) and a homozygous recessive (aa) organism?
50% ## Footnote The Punnett square shows that **50%** of the offspring will inherit the dominant allele (A) from the heterozygous parent, resulting in a dominant phenotype (Aa).
63
# True or False: Females must inherit **two** copies of a recessive allele on the X chromosome for the recessive sex-linked trait to be expressed.
True ## Footnote Females have two X chromosomes, so they need two copies of the recessive allele (one on each X) to express the recessive sex-linked trait, such as color blindness.
64
What does a **pedigree chart** represent?
A family tree that shows the **inheritance of traits across generations**. ## Footnote Pedigrees are used to track the *inheritance* of specific traits, showing the genotypes of family members and how traits are passed through generations.
65
What is the **probability** of a child inheriting a recessive trait from two heterozygous (Aa) parents?
25% ## Footnote The Punnett square shows a **25%** chance (aa) of inheriting two recessive alleles, resulting in the expression of the recessive trait.
66
# Fill in the blank: A \_\_\_\_\_\_\_\_ cross is a genetic cross involving **two** traits.
Dihybrid ## Footnote A *dihybrid cross* tracks two traits, such as seed color and shape, to observe how they assort independently.
67
# True or False: In a monohybrid cross, **two** traits are observed.
False ## Footnote A monohybrid cross focuses on a **single** trait, while a dihybrid cross examines the inheritance of two traits simultaneously.
68
What is the **probability** of offspring inheriting a dominant trait from a homozygous dominant (AA) and heterozygous (Aa) parent?
100% ## Footnote All offspring will inherit at least **one** dominant allele (A), resulting in the expression of the dominant trait.
69
# Define: Incomplete dominance
A genetic scenario where the heterozygote displays an **intermediate phenotype**. ## Footnote In incomplete dominance, *neither* allele is completely dominant over the other, leading to an intermediate expression of traits. For example, crossing red and white flowers may result in pink flowers.
70
What is **codominance**?
Inheritance where **both** alleles are expressed in the heterozygote. ## Footnote Codominance occurs when both alleles contribute equally and visibly to the phenotype. An example is the AB blood group, where both A and B alleles are expressed.
71
# True or False: In incomplete dominance, the heterozygote phenotype is a **blend** of the two homozygotes.
True ## Footnote In *incomplete dominance*, the offspring’s phenotype is a blend of the parental traits, such as pink flowers from red and white flower parents.
72
What would be the **phenotype** of a red-flowered (RR) and white-flowered (WW) snapdragon cross in incomplete dominance?
Pink flowers (RW) ## Footnote Since neither allele is dominant, the resulting phenotype is a **blend** of the two homozygotes, resulting in pink flowers.
73
In the case of a black (BB) chicken and a white (WW) chicken, what would be the **phenotype** of their offspring?
Black and white feathers. ## Footnote In *codominance*, both black and white alleles would be expressed equally in the offspring, resulting in speckled feathers.
74
# True or False: In a cross between two pink (RW) snapdragons, the expected phenotypic **ratio** is 1 red, 2 pink, and 1 white.
True ## Footnote The Punnett square for two RW parents shows a 1:2:1 phenotypic ratio: 25% red (RR), 50% pink (RW), and 25% white (WW).
75
What is a **mutation**?
A **change** in the DNA sequence. ## Footnote Mutations can occur naturally or due to environmental factors like radiation, chemicals, or viruses. These changes can lead to genetic variation, which may or may not affect an organism’s *traits*.
76
What are the **two main types** of mutations?
1. Gene mutations 2. Chromosomal mutations ## Footnote Gene mutations affect a single gene, while chromosomal mutations involve changes to the structure or number of chromosomes.
77
# True or False: Mutations **always** result in harmful effects.
False ## Footnote While mutations can be harmful, beneficial, or neutral, not all mutations result in negative outcomes. Some mutations may even provide advantages in certain environments.
78
What is a **point mutation**?
A mutation that **affects** a single nucleotide in DNA. ## Footnote Point mutations can change one base pair in the gene sequence, potentially altering the protein product. Examples include silent mutations, missense mutations, and nonsense mutations.
79
# Define: Frameshift mutation
A mutation that **shifts** the reading frame of the gene. ## Footnote Frameshift mutations *occur* when nucleotides are inserted or deleted, causing the sequence to shift and change the downstream codons, which can significantly affect the protein’s function.
80
# Fill in the blank: \_\_\_\_\_\_\_\_\_ mutations **result** in the loss or addition of one or more nucleotides in the DNA sequence.
Frameshift ## Footnote Frameshift mutations can have severe effects, potentially leading to a completely different protein being made or no protein at all.
81
# True or False: **Mutations** in genes can lead to changes in traits.
True ## Footnote Mutations are changes in the DNA sequence that can **alter** the structure or function of proteins, resulting in new traits.