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Science Exam Revision Y10 > DNA & Inheritance > Flashcards

DNA & Inheritance Flashcards

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1
Q

What is DNA?

A

Deoxyribonucleic acid (DNA) is the molecule that stores and transmits genetic information that determines the characteristics of all living things. These characteristics are heritable.

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2
Q

What is a DNA structure

A

It has a double helix structure

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3
Q

Where is DNA located

A

Is located in the nucleus of eukaryotic cells.

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4
Q

Draw a DNA Structure Diagram

A

Slide 14

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5
Q

What are the Nitrogenous Bases (Aka Amino Acids)

A

Gaunine and Cytosine
Thymine and Adenine

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6
Q

What is the sugar phosphate backbone

A

Refering to Nucleotides
The phosphate attaches to the sugar of the next nucleotide, creating a ‘backbone’ of alternating phosphates and sugars, forming a strand of DNA.

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7
Q

What is the three subunits for a nucleotide?

A

A deoxyribose sugar.
A phosphate group.
One of four nitrogenous bases (amino acids):
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

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8
Q

What are the Complimentary Base Pairings

A

A pairs with T
G pairs with C
These are pairable. If we think like a jigsaw puzzle, only those pieces connect with one another.

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9
Q

What are Genes?

A

A gene is a section of DNA along a chromosome. Each gene will code for a specific protein.

Genes are the basic functional unit of heredity (the transmission of genetic traits from one generation to the next).

Different genes vary in length from each other (the number of bases).

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10
Q

What are Chromosomes?

A

A chromosome is a thread-like structure composed of DNA and proteins found in the nucleus of a cell.

Chromosomes carry genetic information in the form of genes, which are segments of DNA that code for specific traits or functions.

Every cell of an organism has the same number of chromosomes.

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11
Q

Homologous Chromosomes

A

These are a pair of chromosomes that carry the same genes in the same order, although they may have different versions (alleles) of those genes.

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12
Q

What is an Autosome

A

Chromosomes NOT involved in determining the sex of the individual. Carries genetic information such as eye colour, height and blood type. Humans have 44 autosomes (22 pairs).

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13
Q

What is a Centromere

A

This is a region of the chromosome where the two sister chromatids are joined together and where the spindle fibers attach during cell division.

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14
Q

How many Chromosomes does a human have?

A

Humans have 46, but it is often expressed as 23 pairs because each chromosome is a diploid.
The pairs are the same:
Size
Shape
Banding pattern
provide information for the same characteristics.

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15
Q

Autosome Chromosomes are?

A

Chromosomes not involved in determining the sex of an organism are called non-sex chromosomes (autosomes).

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16
Q

How many Autosome Chromosomes do we have?

A

Humans have 44 (22 pairs) of non-sex chromosomes (Homologous chromosomes).

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17
Q

What are the Sex Chromosome Combinations?

A

two X chromosomes (females)
one X chromosome and one Y chromosome (males).

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18
Q

Proteins are?

A

Genes code for specific proteins. Proteins are large molecules composed of chains of amino acids. They perform a wide variety of functions in the body.

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19
Q

What is DNA Replication?

A

DNA replication is the mechanism for copying (doubling) the DNA. It occurs in the nucleus of the cell.

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20
Q

Is DNA Replication semi-conservative?

A

DNA replication is semi-conservative because each double strand of DNA consists of:
One old template strand
One new complementary strand.

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21
Q

How Does DNA Replication work?

A

The enzyme helicase breaks the hydrogen bonds between the complementary bases joining the two strands.

Each strand serves as a template for making a new strand which is complementary to the template strand .

DNA nucleotides base-pair to the exposed bases A-T or G-C.

Enzymes (known as DNA polymerases) link the nucleotides to the newly forming strand.

Each new double stranded DNA molecule rewinds into a double helix.

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22
Q

DNA replication occurs before…

A

DNA replication occurs before cell division

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23
Q

Why is DNA Replication important?

A

This is an important step before mitosis to ensure each new cell (called a daughter cell) has a complete copy of the genetic material from the parent cell.

This results in the daughter cells containing the same number of chromosomes and the same amount of DNA as the original cell.

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24
Q

Look at DNA Replication Diagram in book

A
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25
Mitosis is?
Mitosis is a type of cell division that occurs in somatic cells (non sex cells).
26
What happens during mitosis?
During mitosis, a single cell divides into two identical daughter cells.
27
Why is Mitosis important?
This process is essential for: growth repair maintenance of tissues and organs in multicellular organisms.
28
Mitosis VIDEO!! From ANOEBA SISTERS!
29
Mitosis stages
IPMAT+C Interphase Prophase Metaphase Anaphase Telophase + Cytosine
30
Interphase
This is the ‘pre-mitosis’ phase. It is where the parent cell’s DNA is replicated so that two copies exist. Isolate!
31
Prophase
This is where the nuclear membrane of the parent cell breaks down and the (already copied) chromosomes condense and become visible under a microscope. At this stage, each chromosome consists of a pair of identical chromatids joined by a structure called a centromere. Long protein filaments called spindle fibres are formed between the two centrioles to form a structure known as the spindle. PREPARE!!
32
Metaphase
This stage is where the pair of chromatids are gradually moved to the equator of the cell by the spindle fibres. MIDDLE!!
33
Anaphase
This is where chromatid pairs are separated to form two identical sets of daughter chromosomes. Each daughter chromosome set is then moved to the poles of the spindle by the spindle fibres. Away!!!
34
Telophase
This is where the spindle breaks down and the set of chromosomes at each pole of the spindle de-condense and become enclosed by a nuclear membrane.
35
Cytokinesis
This stage occurs near the end of telophase. In animal cells protein fibres in the cell membrane constrict to form an infolding called a -> cleavage furrow. <- More constriction leads to production of two genetically identical diploid daughter cells.
36
Meiosis is?
Meiosis is the process of cell division that produces the gametes - sex cells (sperm and eggs).
37
How many cells does Meiosis make?
Meiosis creates daughter cells with exactly half as many chromosomes as the starting cell. By the end of the process, four daughter cells are created
38
Diploid is...?
cell with two sets of chromosomes (2n)
39
Haploid is...?
a cell with a single set of chromosomes (n).
40
Meiosis is... [diploid and haploid definition]?
Meiosis is the division process of going from a diploid cell to a haploid cell. In humans, the haploid cells are sperms and eggs. When a sperm fuses with an egg during fertilization, the two haploid sets of chromosomes form a diploid set.
41
How does Haploid Gametes become a Diploid.
Two haploid gametes (sex cells) fuse to restore the diploid chromosome number in the zygote (fertilised cell).
42
What do Chromosomes do Gametes have.
Sperm contains genetic material from the father → 22 autosomal chromosomes and 1 sex chromosome. Egg contains genetic material from the mother → 22 autosomal chromosomes and 1 sex chromosome.
43
Meiosis Process
Firstly, the chromosomes replicate in preparation for cell division just as they do in mitosis. However, the chromosomes then form up into their homologous pairs. Once these pairs are formed, a process called crossing over occurs, where there will be a random exchange of genes within the pairs of chromosomes (which we will discuss later). Once the crossing over process has been completed, the cell begins to divide into two daughter cells. During this process, one chromosome from each homologous pair is randomly distributed to each of the two daughter cells in a process called independent assortment. Finally, the two new daughter cells undergo further cell division, which produces a total of four haploid daughter cells.
44
The difference between meiosis and mitosis
Mitosis produces two diploid daughter cells, which are identical copies of the parent cell. Occuring only in Somatic Cells. Happens for repair, maintanence and growth. Meiosis produces haploid four daughter cells, each containing half of their original parent cell’s DNA. Occuring only in Gametes. only for sexual reproduction
45
What causes Genetic Variation? What is Genetic Variation?
Due to meiosis, sexual reproduction results in nearly infinite possibilities of genetic variation, which is vital to the survival of species. In other words, sexual reproduction results in offspring that are genetically unique. This occurs mainly due to crossing over and independent assortment. Crossing-over is the exchange of genetic material between homologous chromosomes. It results in new combinations of genes on each chromosome. The points where homologous chromosomes cross over and exchange genetic material is random.
46
Diploid Chromosomes are...?
Definiton: Two sets of Chromosome (one from each parent) Represented as: 2n Number of chromosomes: Humans have 46 chromosomes (23 pairs) Found in: Most somatic (body) cells Formation: Results from the fusion of two haploid gametes during fertilization Role: Determines traits, controls cell functions, and enables growth Examples: Skin cells, muscle cells, blood cells
47
Haploid Chromosomes are...?
Definition: One set of chromosomes Represented as: n Number of chromosomes: Humans have 23 chromosomes Found in: Gametes (sex cells) Formation: Produced by meiosis, a type of cell division that halves the chromosome number Role: Essential for sexual reproduction, and the creation of genetic diversity Examples: Sperm cells, egg cells
48
Independent Assortment is..?
When cells divide during meiosis, homologous chromosomes are randomly distributed to daughter cells.
49
What is responsible for splitting DNA during the DNA replication process.
DNA Helicase Enzyme
50
Somatic Cell..?
any cell other than a gamete
50
Zygote...?
Fertilized egg cell
51
What are the three Medallion Genetic Principles
The inherited traits are determined by genes that are passed from parents to children. A child inherits two sets of genes—one from each parent. A trait may not be observable, but its gene can be passed to the next generation.
52
Alleles are...?
Every organism inherits two copies of every gene. A set of genes from the father (paternal) and a set of genes from the mother (maternal). The variations in a gene - different traits, are known as alleles.
53
Allele Notation. How to know if an allele is dominant or recessive.
A capital letter represents a trait (gene) that is dominant. A lowercase letter represents a trait that is recessive. This means it is less likely to be expressed.
54
Phenotype...?
The phenotype is the allele that is expressed (observed). These are generally dominant. For example, your eye colour is the phenotype
55
Genotype...?
The genotype is the genetic information inherited from both parents for that gene. It results in specific phenotype.
56
Homozygous...?
Homozygous genotypes refers to an individual that has inherited the same alleles from both parents. If Brown eyes = B and Blue eyes = b Homozygous genotypes (same) = BB or bb
57
Heterozygous...?
Heterozygous genotypes are when the individual has inherited a different allele from each parent. If Brown eyes = B and Blue eyes = b Heterozygous genotypes (different) = Bb
58
Complete Punnet Square Sheet
59
Check Punnet Squares in Book
60
Sex-Linked Inheritance is what?
Sex linked inheritance refers to traits that arise from genes which are located on the sex chromosomes (X or Y). (Remember Males = XY, Females = XX). Sex linked traits are more prevalent in males because males inherit all X linked genes from their mother. If a male inherits an X linked trait (recessive or dominant) it will be expressed because he has no other X chromosome to prevent the gene from being expressed. Check book for the diagram
61
Slide 121
62
What are the three steps to DNA Replication in order?
Slide 50-53
63
What is the smallest living unit
Cell
64
What is a Somatic Cell
cells in the body other than sperm and egg cells. Key word being Cells
65
How many chromosomes do Somatic Cells have
A diploid number of chromosomes aka two sets of chromosomes one from each parent.
66
What is a phenotype
A trait that is expressed or seen
67
What is a Gene
A section of DNA that codes for a specific trait is called
68
Having two identical alleles for a trait
Homozygous
69
Having two different alleles for a trait
Heterozygous
70
Dominant or Recessive? TT
Dominant
71
Dominant or Recessive? Tt
Dominant
72
Dominant or Recessive? tt
Recessive
73
Trait is a ?
A physical characteristic of an organism
74
Genotype is ...?
alleles present for a trait
75
Allele is...?
an alternative form of a gene
76
Hereditary is..?
Passing of traits from parents to offspring
77
Draw a Punnet Square !!!
78
Chromotids
A chromotids refers to duplicated Chromosomes chromosomes. For instance, 'I' is a chromosome whilst 'II' is SISTER CHROMOTIDS
79
How do Genes and Chromosomes link to DNA?
Cell > Nucleus > Chromosome > Gene > DNA Try drawing it
80
Why is DNA Semi-Conservative
Because it retains one old strand of DNA and one new strand of DNA
81

Science Exam Revision Y10 (3 decks)

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