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Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

Heredity

A

Passing of traits from parents to offspring

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2
Q

Genetics

A

is the study of heredity and variation

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3
Q

In a chromosome, genetic information is stored in a molecule of________

A

DNA

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4
Q

DNA

A

Has set of chemical instructions for the cell; a gene

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5
Q

Gene

A

Portion of DNA that contains information that helps produce trait

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6
Q

locus (plural - loci)

A

Each gene occupies a specific location on a chromosome

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7
Q

Nucleic acids

A

Are long polymers that hold information to specify the structure of proteins to be made in a cell

These determine the characteristics and functions a cell will have

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8
Q

Structure of nucleic acids

A

Made of subunits called nucleotides

Nucleotides are made up of 3 smaller building blocks

  1. Five Carbon sugar ( in a ring )
  2. Phosphate group
  3. Nitrogen Base
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9
Q

What are the 2 types of Nucleic Acid?

A
  1. DNA

Found in the nucleus and is the main component of genes

The sugar in the nucleotides are called deoxyribose sugar (missing oxygen from 2nd carbon)

Adenine —> Thymine

Guanine —> Cytosine

  1. RNA

Also found in the nucleus, and contains instructions for making proteins.

The sugar in the nucleotides is called ribose sugar.

Guanine —> Cytosine

Adenine —> Uracil`

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10
Q

2 types of Nitrogen Bases

A

Purines: Adenine and Guanine (large, double-ringed compounds)

Pyrimidines: Cytosine and Thymine (smaller, single-ringed compounds)

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11
Q

Chromatin

A

thread-like structure made up of DNA and proteins in the nucleus of a eukaryotic cell

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12
Q

Chromosome

A

structure in the nucleus of a eukaryotic cell that carries genes, formed when chromatin condenses

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13
Q

Chromatid

A

each of the two identical chromosome strands in a replicated chromosome attached by their shared centromere

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14
Q

Cells reproduce through controlled growth and division for 3 main functions:

A

Growth

Maintenance to replace dead/dying cells

Repair of tissues/organs

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15
Q

what are the 3 stages of cell cycle

A

Interphase

Mitosis

Cytokinesis

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16
Q

Interphase

A

Period between cell divisions

Cell undergoes growth, duplicates hereditary information and prepares for mitosis

Most of cell life is in this stage, misnamed as “resting phase”

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17
Q

What phases is Interphase broken down into? and describe each phase.

A

G1 phase (first gap): cell is growing and preparing for replication

S phase (synthesis): genetic information is replicated

G2 phase (second gap): final preparation for cell division

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18
Q

Once cell begins to divide:

A

The nucleus must undergo mitosis

Cytokinesis occurs at the end of the cycle

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19
Q

Mitosis

A

stage of the cell cycle during which genetic information is divided equally into 2 nuclei

Occurs in somatic cells

Any cell that is not a reproductive cell

Occurs in most tissues that must replace themselves (eg. skin)

Occurs when a parent cell divides to produce two daughter cells

Daughter cells are genetically identical to parent

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20
Q

What are the phases of mitosis?

A

Prophase, Metphase, Anaphase, Telophase

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21
Q

Prophase

A

Chromatin condenses into chromosomes, join at the centromere

Nuclear envelope breaks down

Centrioles move to poles, producing microtubules (spindle fibres)

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22
Q

Metaphase

A

Spindle fibres begin moving and aligning chromosomes

Chromosomes line up along the equator (metaphase plate)

Chromosomes are condensed and thick

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23
Q

Anaphase

A

sister chromatids separate from one another producing 2 single stranded chromosomes

Spindle fibres shorten as they pull the chromosomes to opposite poles

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24
Q

Telophase

A

Chromosomes decondense

Spindle breaks down

Nuclear envelope forms

Cleavage furrow begins in animal cells or cell plate forms in plant cells

Mitosis ends with telophase

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25
Q

Cytokinesis

A

Division of cytoplasm

Cleavage furrow pinches off

Formation of two identical daughter cells

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26
Q

Somatic Cells

A

body cells, that have a diploid number of chromosomes (two sets)

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27
Q

Cancer

A

Abnormal cell division; out of control, continuous

28
Q

What are the 2 types of Tumors? And describe each of them

A

Benign tumours show no signs of spreading

Malignant tumors are capable of spreading and invading new tissues (metastasis)

29
Q

How can you treat cancer?

A

Therapy: radiation, chemotherapy, immunotherapy

30
Q

Sister Chromatids

A

are when two chromatids are held together by a centromere (they are called sister chromatids because they contain the same type of genes on them) -> “double-stranded” chromosome

31
Q

Homologous Chromosomes

A

matching pairs of chromosomes, similar in size and shape and have the same genes, arranged in the same order

Consist of a chromosome from the male parent and a chromosome from the female parent.

32
Q

Meiosis

A

Only occurs in eukaryotes that reproduce sexually

Only occurs in organisms that are at least diploid

Undergoes TWO divisions

1 parent cell produces 4 gamete cells

Each gamete cell contains different genetic information

33
Q

What does the creation of gametes rely on?

A

The creation of gametes relies on meiosis, a specialized process of cell division that produces gametes!

34
Q

How many stages are there in meiosis

A

The process of meiosis, involves two stages of cell division which in turn reduces the number of chromosomes to half the amount present (becomes haploid).

35
Q

Premeiotic Interphase

A

DNA replicates

Two identical copies of each chromosome are made, attached at centromere

Each copy is called a sister chromatid

36
Q

Prophase I

A

Homologous chromosomes pair together, called a tetrad (each chromosome made of 4 chromatids held together by kinetochore)

Each sister chromatid intertwines with a sister chromatid from matching homologous chromosomes, called synapsis

Once synapsis occurs, intertwined chromatids from different chromosomes break and reattach to each other

CROSSING OVER: Results in recombination of genetic information between non sister chromatids, at random points called chiasmata

Centrioles move to opposite poles, and spindle fibres appear

37
Q

Metaphase I

A

Spindle fibers attach to kinetochore of tetrad

Tetrads line up along equatorial plate (middle)

Independent assortment occurs

Randomly lines up in the middle

38
Q

Anaphase I

A

Tetrad is pulled apart as each chromosome moves towards the opposite pole

Chromosomes are pulled apart at the kinetochore

Sister chromatids are still intact

39
Q

Telophase I

A

Chromosomes reach poles

Nuclear membrane reforms

Spindle fibres disintegrate

40
Q

Cytokinesis for meiosis

A

Cytoplasm and organelles divide in half

Each daughter cell is haploid (n)

One chromosome from each original homologous pair, HOWEVER, sister chromatids still exist

41
Q

Second Meiotic Division: Meiosis II

A

There is no replication of DNA (interphase II)

Chromosomes in daughter cells of meiosis I are in the form of sister chromatids

No crossing over occurs (no homologues to synapse)

42
Q

Prophase II

A

Chromosomes condense

Centrioles move to opposite poles

Spindle fibres appear

43
Q

Metaphase II

A

Sets of chromatids move to equator

Centromeres divide

44
Q

Anaphase II

A

Chromatids move to opposite poles

45
Q

Telophase II

A

Chromosomes unwind, and nuclear envelope forms.

Produces 4 haploid cells (sperm or ova) after cytokinesis

46
Q

Cytokinesis II

A

Product: 4 cells, each with a haploid amount of chromosomes

They are all genetically different!

47
Q

2 Methods of Genetic Variability in Meiosis

A

During Metaphase I of meiosis, homologous chromosome pairs separate randomly.

Some gametes may receive all paternal chromosomes or all maternal or a mixture of both.

Meiosis is an important source of GENETIC VARIABILITY!

Another way in which meiosis contributes to variability is from crossing over during prophase I

48
Q

Gamete Formation (Gametogenesis)

A

At the end of meiosis, gametes are formed which differentiate into specialized cells

Sperm formation (spermatogenesis):

Diploid spermatogonia → primary spermatocytes → 4 spermatids

Egg formation(oogenesis):

Diploid Oogonia → primary oocytes → 1 egg + 3 polar bodies

49
Q

Aneuploidy

A

Error in meiosis

Occurs when chromosomes do not separate properly during meiosis leading to cells having too many or too few chromosomes

50
Q

Nondisjunction

A

Failure of homologous chromosomes to separate in meiosis I

Failure of sister chromatids to separate in meiosis II

51
Q

Monosomy

A

fertilized cell is missing a chromosome

52
Q

Trisomy

A

fertilized cell has an extra copy of a chromosome

53
Q

Polyploidy

A

Every chromosome is duplicated

Can be 3n, 4n , etc

54
Q

Nondisjunction Disorders

A

Results in cells not being able to function properly

Responsible for a lot of human genetic disorders

Eg. Down’s syndrome (trisomy 21): result of nondisjunction of chromosome 21.

The offspring receives 3 copies instead of 2.

An excess of genetic information causing people with this disorder to have mental and physical differences/challenges

55
Q

List some of the Nondisjunction Disorders

A

Responsible for:

Down Syndrome (trisomy 21)

Physical/mental challenges

Turner Syndrome (One X chromosome)

Females born sterile

Klinefelter Syndrome (2 X and 1 Y chromsomes)

Males usually sterile; display feminine traits

Patau Syndrome (trisomy 13)

Developmental problems (brain, kidney, heart)

56
Q

Karyotyping

A

Karyotyping can be used to diagnose chromosomal abnormalities prenatally

Cells for testing can be collected from the amniotic fluid (amniocentesis) or from villi along the lining of the uterus (chorionic villus)

Scientists count, compare, arrange chromosomes to see if there are any issues

Normally recommended for women over the age of 35

57
Q

Why is a karyotyping important for women over the age of 35?

A

May be due to oocytes stopping at prophase I until ovulation as part of oogenesis

This results in a higher change for nondisjunction in meiosis I from older organelles which age with the individual

58
Q

Inheritance

A

is the process of genetic transmission of a trait/characteristic from parent to offspring.

59
Q

Allele

A

A specific form of a gene (eg. purple flower, white flower)

60
Q

homozygous

A

If an individual has two of the same alleles (eg. both dominant or both recessive)

61
Q

heterozygous

A

If an individual has two different alleles (eg. one dominant, one recessive) it is considered

62
Q

Genotype

A

genetic makeup of alleles

63
Q

Phenotype

A

appearance of a trait

64
Q

What is the purpose of monohybrid crosses?

A

Mendel recorded his observations of peas using thousands of monohybrid crosses.

These crosses are between two organisms (in this case pea plants) with only ONE characteristic that is different.

Monohybrid crosses illustrate all of the possible combinations of gametes from a given set of parents.

They are used to calculate the probability of inheriting a particular trait.

65
Q

Law of Segregation

A

Organism inherits 2 copies of genes, one from each parent

Organism only donates one copy of each gene

66
Q

Law of Independent Assortment

A

Law of Independent Assortment states that if genes are on separate chromosomes, they are inherited independently of each other (unlinked)

67
Q

dihybrid cross

A

A dihybrid cross determines genotypic and phenotypic combinations of offspring for two particular genes that are unlinked.

Two genes, each have two alleles, there can be up to four gamete combinations per parent

Biology (7 decks)

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