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Biology Unit 2A: Flashcards

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1
Q

Is DNA always identical or does it depend, what shape is it in?

A

DNA is always identical, always in a double helix

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2
Q

Name what is made up of the DNA strand left to right

A

Phosphate molecule, weak hydrogen bond, sugar molecule

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3
Q

Does a chromosome carry one of two traits and are they coiled or not?

A

Chromosomes carry 1 trait and are coiled

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4
Q

What is a chromosome?

A

Made of DNA and protein it carries genetic information from cell or cell.

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5
Q

What is a gene

A

A gene is a short segment of DNA that controls the expression of a trait

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6
Q

What are the actions of the gene

A
  1. Gene has instructions of make 1 protein
  2. Proteins form all the enzymes and strucutres
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7
Q

Why are many hormones proteins and what do they transport

A

This is because they transport materials across membranes

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8
Q

1 genetic trait controlled by 1 gene, and 1 genetic trait controlled by multiple genes.

A
  1. Being lactose intolerant is controlled by 1 gene
  2. Your body shape is controlled by multiple
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9
Q

Name the whole DNA structure

A

Protein is twisted like a helix outside, while the gene are lined up between.

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10
Q

Explain somatic cells

A

Somatic = Body cells

Diploid = 2 sets (46 chromosomes total, 23 pairs)

Made by mitosis = Exact copies

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11
Q

Explain sex cells

A

Sex cells also known as gametes are either the egg or the sperm they have 23 chromosomes each and will combine to make the total 46. They are haploid. They are made through a process called miosis

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12
Q

What are the three main functions of mitosis in multicellular organisms?

A
  1. Allows growth by creating new cells

2 . Replaces damaged or dead cells (e.g., healing wounds).

  1. Asexual Reproduction – Enables some organisms to reproduce without gametes (e.g., bacteria, plants, and some animals).
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13
Q

What is asexual reproduction, and how does it relate to mitosis?

A

Asexual reproduction is a process where offspring arise from a single parent and inherit identical genetic material. Mitosis is the mechanism by which single-celled organisms reproduce asexually and multicellular organisms grow and repair tissues.

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14
Q

What is the key difference between asexual and sexual reproduction?

A

Asexual reproduction produces genetically identical offspring from a single parent, while sexual reproduction involves two parents, leading to genetic variation due to the combination of gametes.

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15
Q

What are the two major stages of the cell cycle, and what happens in each?

A

Interphase (95% of the cycle) – The cell grows, performs normal functions, and prepares for division.

Mitosis (5% of the cycle) – The nucleus divides, ensuring each daughter cell gets identical genetic material.

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16
Q

What are the three stages of interphase, and what happens in each?

A

G₁ (Gap 1 Phase) – The cell grows and performs normal metabolic activities.

S (Synthesis Phase) – DNA replication occurs, producing identical sister chromatids.

G₂ (Gap 2 Phase) – The cell prepares for mitosis, producing proteins and organelles.

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17
Q

What is chromatin, and how does it change throughout the cell cycle?

A

Chromatin → Chill (loose, uncoiled in interphase)

Chromosomes → Compact (condensed for mitosis)

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18
Q

What is the purpose of mitosis?

A

Mitosis ensures the accurate division of the nucleus, producing two genetically identical diploid daughter cells for growth, repair, and asexual reproduction.

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19
Q

What are the four phases of mitosis, and what is a mnemonic to remember them?

A

PMAT
Prophase
Metaphase
Anaphase
Telephase

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20
Q

What major events occur during prophase?

A

Chromosomes are starting to condense still just scattered in the nucleus

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21
Q

What happens during metaphase, and why is it important?

A

The sister chromosomes are lined up in the middle, the nucleus is gone, spindle fibers on the sides

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22
Q

What happens during Anaphase?

A

During anaphases the chromosomes move towards the sides of the cell splitting apart, the spindle fibers are pulling them.

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23
Q

What happens during telophase?

A

Nucleus forms around the 2 set of chromosomes, forming 2 new cells.

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24
Q

what happens during Cytokinesis?

A

Splits the cytoplasm, this forms 2 new cells both with 46 chromosomes, officially ending mitosis.

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25
What are the building blocks of DNA?
Nucleotides, each consisting of a sugar, a phosphate group, and a nitrogen base.
26
What are the four nitrogen bases in DNA?
Adenine (A), Guanine (G), Cytosine (C), Thymine (T).
27
What does "antiparallel strands" mean in DNA?
The two nucleic acid strands run in opposite directions, with one being "upside down" compared to the other.
28
How are DNA strands held together?
By hydrogen bonds between complementary nitrogen base pairs.
29
What is a karyotype?
A picture of an individual's set of chromosomes, used to diagnose genetic disorders.
30
What is an allele?
A variation of a gene (e.g., hair color alleles: black, brown, blond, red).
31
What are homologous chromosomes?
Pairs of chromosomes that are identical in length, centromere location, and banding pattern. ( Basically both pair of chromsomes are 1 parent and 1 is the other parent and they are indentical)
32
How many pairs of chromosomes do humans have?
23 pairs—22 pairs of autosomes and 1 pair of sex chromosomes.
33
When are chromosomes diploid and unreplicated?
In somatic cells during the beginning of interphase.
34
When are chromosomes diploid and replicated?
n somatic cells during prophase and in precursor cells (spermatogonium, oogonium).
35
What is a haploid cell?
A cell with unreplicated (single-stranded) chromosomes, such as a gamete (sperm or egg).
36
What does "n" represent in genetics?
"n" is the number of unique chromosomes in a haploid set. Humans have n = 23, meaning: Gametes (sperm/egg) are haploid (n = 23). Somatic (body) cells are diploid (2n = 46).
37
How are chromosomes arranged in a karyotype chart?
By size, banding pattern, and centromere position, from largest to smallest.
38
What is a diploid cell?
A cell with two sets of chromosomes (2n), one from each parent. Example: human body cells (46 chromosomes).
39
What is a haploid cell?
A cell with one set of chromosomes (n). Example: human gametes (sperm/egg) with 23 chromosomes.
40
What are the three steps of DNA replication?
Think of a road trip 🚗: 1️⃣ Initiation – Start the car (begin the process) 2️⃣ Elongation – Drive along the highway (keep going) 3️⃣ Termination – Park the car (end the process)
41
What happens during initiation?
The DNA unzips to form a replication fork.
42
What happens during elongation?
Complementary base-pairing occurs on both unzipped parent strands.
43
What happens during termination?
New strands are ligated into a continuous double strand. DNA rewinds into a double helix. The semi-conservative model ensures each new DNA molecule has one old and one new stran
44
What does "semi-conservative" replication mean?
Each new DNA molecule has one old strand and one newly synthesized strand.
45
What is meiosis?
Meiosis is the process by which sex cells (gametes) are made, reducing the chromosome number by half to form haploid cells.
46
What happens when a haploid sperm fertilizes a haploid egg?
A diploid zygote is formed, which is the first body cell.
47
What are the two stages of meiosis?
Reduction division—one diploid cell forms two haploid cells by separating homologous chromosomes. Meiosis II: Each haploid cell divides again by separating sister chromatids.
48
What is the key event in Prophase I of meiosis?
Homologous chromosomes pair up to form tetrads, and crossing-over may occur.
49
What is the difference between Metaphase I and Metaphase II?
Metaphase I: Homologous chromosome pairs (tetrads) line up in a double line. Metaphase II: Chromosomes line up in a single line, like in mitosis.
50
What is the result of Anaphase I?
Homologous chromosomes are separated and pulled to opposite ends of the cell, reducing the chromosome number.
51
How many cells are formed at the end of meiosis?
Four haploid cells.
52
How does meiosis differ in males and females?
Males (Spermatogenesis): Produces 4 sperm cells. Females (Oogenesis): Produces 1 egg and 3 polar bodies.
53
What are the key differences between mitosis and meiosis?
Mitosis: Produces 2 diploid, genetically identical cells. Meiosis: Produces 4 haploid, genetically different cells. Mitosis is a cycle; meiosis is not.
54
Draw meiosis
55
What is spermatogenesis?
Spermatogenesis is the process where diploid germ cells in the testes undergo meiosis to form four haploid sperm cells.
56
What is oogenesis?
Oogenesis is the process where a diploid germ cell in the ovary undergoes meiosis to form one haploid ovum and two (or three) haploid polar bodies.
57
What happens during fertilization?
A haploid sperm (N) enters a haploid egg (N), forming a diploid zygote, which is the first somatic cell.
58
What are four methods that increase genetic variation?
1️⃣ Independent Assortment → Chromosomes mix randomly during meiosis. 🎲 2️⃣ Crossing Over → Chromosomes swap pieces for variety. 🔄 3️⃣ Non-disjunction → Chromosomes fail to separate properly. ❌ 4️⃣ Structural Mutations → Chromosome parts change (delete, duplicate, etc.). 🏗️Independent s
59
What is the Law of Independent Assortment?
Chromosomes segregate independently when gametes are formed during meiosis, ensuring genetic diversity.
60
How does crossing-over contribute to genetic variation?
During Prophase I of meiosis, homologous chromosomes exchange segments, increasing genetic diversity.
61
What is non-disjunction?
Non-disjunction occurs when chromosomes fail to separate properly during meiosis, leading to genetic disorders.
62
What are the three types of non-disjunction mutations?
Monosomy: Missing a chromosome Trisomy: Extra chromosome (e.g., Down’s syndrome) Polyploidy: Extra sets of chromosomes (common in plants)
63
What are the four types of structural chromosomal mutations?
Deletion – A chromosome segment is removed. Duplication – A chromosome segment is repeated. Inversion – A segment is reversed in the chromosome. Translocation – A chromosome segment moves to a non-homologous chromosome.
64
How do mutations affect offspring?
Mutations in gametes are passed to every cell of the offspring. They can be harmful, neutral, or beneficial.

Biology (2 decks)

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