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Biology HSC 2021 > Assessment 1 > Flashcards

Assessment 1 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Pedigrees Symbols:

A 
Males= Squares
Females= Circles
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2
Q

What is used to signify an infected individual on a pedigree?

A

shading

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3
Q

Why are pedigrees helpful?

A

Pedigrees are valuable tools in genetic counselling. It allows a pattern of inheritance to be traced through generations of a family.

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4
Q

Pedigrees: of a dominant trait

A

heterozygous individuals will be affected and two affected parents can produce an unaffected child

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5
Q

Pedigrees: of a recessive trait

A

heterozygous parents will be unaffected, two affected parents will always have an affected child

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6
Q

What is incomplete dominance?

A

n incomplete dominance a heterozygous individual blends the two traits

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7
Q

Do mendelian ratios apply to incomplete dominance?

A

Yes

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8
Q

What is the cell cycle?

A

Most cells grow, perform the activities needed to survive and divide to create new cells. This is replicated throughout the life of a cell.

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9
Q

what is the most important stage of the cell cycle?

A

The division portion of the cell cycle is extremely important as this is the point when genetic information is passed to its offspring cells

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10
Q

What does division in the cell cycle ensure?

A

The division ensures that new cells are able to replace the older cells within an organism whenever those cells die

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11
Q

What is mitosis?

A

When the cell nucleus divides into two

One cell replicates in genetic nucleus content exactly and then divides to become two cells

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12
Q

How does mutation occur?

A

if cells divide in an uncontrolled manner, tumour or cancer may result

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13
Q

why is cell division essential?

A

Cell division is essential for the continued growth of organisms and for the repair of damaged/ worn-out cells within them

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14
Q

Mitosis explained (detailed)

A

interphase: DNA has replicated but has not formed the condensed structure of the chromosome. The nuclear membrane is still intact to protect the DNA molecule from undergoing mutation.
Prophase: The DNA molecules progressively shorten and condense by coiling, to form chromosomes. The nuclear membrane is no longer visible. The spindle apparatus has migrated to opposite poles of the cell.
Metaphase: (middle)The spindle fibres attach themselves to the centromeres of the chromosomes and align at the chromosomes at the equatorial plate.
Anaphase: (away) The spindle fibres shorten and the centromere splits, separated sister chromatids are pulled along behind the centromeres.
Telophase: (two) The chromosomes reach the poles of their respective spindles. Nuclear envelope reform before the chromosomes uncoil. The spindle fibres disintegrate.
Cytokinesis: The splitting of the daughter cells. A furrow forms and the cell is pinched in two. Each daughter cell contains the same number and quality of chromosomes.( In plant cells: cytokinesis involves a cell plate while the nucleus is still in telophase).

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15
Q

Mitosis interphase

A

interphase: DNA has replicated but has not formed the condensed structure of the chromosome. The nuclear membrane is still intact to protect the DNA molecule from undergoing mutation.

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16
Q

Mitosis prophase

A

Prophase: The DNA molecules progressively shorten and condense by coiling, to form chromosomes. The nuclear membrane is no longer visible. The spindle apparatus has migrated to opposite poles of the cell.

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17
Q

Mitosis metaphase

A

Metaphase: (middle)The spindle fibres attach themselves to the centromeres of the chromosomes and align at the chromosomes at the equatorial plate.

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18
Q

Mitosis anaphase

A

Anaphase: (away) The spindle fibres shorten and the centromere splits, separated sister chromatids are pulled along behind the centromeres.

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19
Q

Mitosis Telophase

A

Telophase: (two) The chromosomes reach the poles of their respective spindles. Nuclear envelope reform before the chromosomes uncoil. The spindle fibres disintegrate.

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20
Q

Mitosis cytokinesis

A

Cytokinesis: The splitting of the daughter cells. A furrow forms and the cell is pinched in two. Each daughter cell contains the same number and quality of chromosomes.( In plant cells: cytokinesis involves a cell plate while the nucleus is still in telophase).

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21
Q

Mitosis (simple)

A

Interphase- DNA replicated
Prophase- condense and form chromosomes, at opposite poles of the cell
Metaphase- sister chromatids are pulled along behind the centromere
Telophase- Chromosomes reach poles, daughter cells
Cytokinesis- the splitting of the daughter cells

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22
Q

What is meiosis?

A

A form of cell division happening in sexually reproducing organisms by which two consecutive nuclear divisions occur leading to the production of four haploid cells, with the maternal and paternal chromosomes being distributed randomly between the cells.

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23
Q

Meiosis and genetic variation:

A

Genetic variation arises as a result of the behaviour of chromosomes: during the crossover and when chromosomes randomly segregate and paternal and maternal chromosomes assort independently of each other (2 to the power of 23)

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24
Q

Meiosis 1

A

Chromosomes line up in homologous pairs ( one maternal and one paternal) during prophase 1
Crossing over occurs: arms of homologous chromosomes exchange material during metaphase.
Crossing over ensures that linked genes on chromosomes can be inherited independently of each other.
The exchange of genetic material causes the mixing of paternal and maternal genes and results in an increased combination of genes that may be transmitted by gametes to offspring
The chromosomes in each pair of chromosomes separate during anaphase 1, so that entire chromosomes of each pair move into a daughter cell.
The separation (random segregation) ensures the gametes will be half that of the original cell
Independent assortment occurs

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25
Q

What is crossing over?

A

Crossing over occurs: arms of homologous chromosomes exchange material during metaphase.
Crossing over ensures that linked genes on chromosomes can be inherited independently of each other.
The exchange of genetic material causes the mixing of paternal and maternal genes and results in an increased combination of genes that may be transmitted by gametes to offspring

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26
Q

What is random segregation?

A 
The chromosomes in each pair of chromosomes separate during anaphase 1, so that entire chromosomes of each pair move into a daughter cell. 
The separation (random segregation) ensures the gametes will be half that of the original cell
Independent assortment occurs
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27
Q

Meiosis 2

A

The two daughter cells that result from Meiosis 1 undergo meiosis 2, but it does not further affect genetic variation

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28
Q

Stages of meiosis:

A

Early prophase: chromosomes separate out into homologous pairs
Late prophase: Nuclear membrane breaks down, chromosomes split into chromatids and crossing over occurs
Metaphase 1: chromosomes align in pairs in the middle, random segregation
Telophase: Two daughter cells form, chromosome number halved
Cytokinesis 1: Daughter cells are not identical and have half the original number of chromosomes
Metaphase 2: Chromosomes align at the equator
Anaphase 2: Chromatid move apart to opposite poles
Cytokinesis 2: Four resulting daughter cells are not identical to each other and have half the original chromosome number

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29
Q

What is DNA?

A

the genetic material that organisms inherit from their parents.

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30
Q

What is a gene?

A

a discrete unit of hereditary information consisting of a specific section of DNA.
Short lengths of DNA make up genes so genes have the same chemical composition as DNA.

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31
Q

What is a DNA molecule?

A

A DNA molecule is very long and usually consists of hundreds of thousands of genes.

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32
Q

DNA replication basic

A

When a cell reproduces itself by dividing, its DNA is copied and passed along from one generation of cells to the next.
Encoded in the structure of the DNA is information that programs all the cell’s actions

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33
Q

What is a chromosome?

A

Compact coils of thread-like molecules called DNA, organised around proteins called histones
Chromosomes consist of 40% DNA and 60% proteins (histone).

34
Q

genes in chromosomes:

A

Chemically, each gene is made up of a portion of DNA that stores information as a coded sequence, and each coding sequence/gene is located at a particular site or locus on the chromosome

35
Q

What doe the coded info in genes determine?

A

The coded information within genes determines how living things look, behave and function or phenotypes.

36
Q

What are homologous pairs of chromosomes?

A

Maternal and paternal chromosomes that carry alleles of the same genes are known as homologous pairs of chromosomes

37
Q

What happens to the chromatin when cells begin to divide?

A

When cells begin to divide, the chromatin material coils into short, thick, rod-shaped chromosomes for easy transfer

38
Q

What did Watson and crick’s model reveal?

A

They revealed that DNA is a double helix or ‘twisted ladder”

39
Q

What are nucleotides?

A

A DNA molecule is made up of two chains/strands of monomers called nucleotides

40
Q

What does each nucleotide consist of?

A

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

41
Q

What are the bases?

A

Adenine (A), Thymine (T), Guanine (G) and Cytosine (C)

42
Q

How are the bases arranged?

A

The bases are arranged in a sequence along each strand of DNA, each DNA molecule is thousands of bases long
The whole molecule spirals and is therefore known as the double helix
There is a leading strand and a lagging strand

43
Q

Chemical structure of DNA:

A

Each of the two complementary strands in a DNA molecule is made up of a sequence of many nucleotides. The strands are held together by weak hydrogen bond in the centre
The vertical side of the ladder are made up of a sugar-phosphate backbone and the rungs of the ladder are pairs of nitrogenous bases
The 4 bases pair A-T and G-C

44
Q

What is DNA replication?

A

The replication of the long sequences accounts for the replication of the genetic code of an organism
During meiosis and mitosis, it is necessary for the DNA to make an exact replication of itself

45
Q

How does DNA replication occur?

A

The DNA double helix is unwound by the enzyme helicase
The DNA unzips forming two single strands
Nucleotides are attached to the single strands resulting in two identical strands of DNA by DNA polymerase (enzyme). The two double-stranded molecules are chromatids.

46
Q

What do the enzymes do in DNA replication?

A

Primase sends a signal for the starting point for DNA polymerase
Ligase glues together small sections of DNA
This process passes on the genetic information from generation to generation

47
Q

Sexual reproduction DNA replication:

+ fertilisation

A

During sexual reproduction, the genetic code is copied and then half of the genetic information passes into each of the daughter cells
When fertilisation occurs the new organism has half the genetic material from each parent

48
Q

Why does meiosis occur twice?

A

Cells undergoing mitosis just divide once because they are forming two new genetically identical cells whereas in meiosis cells require two sets of divisions because they need to make the cell a haploid cell which only has half of the total number of chromosomes.

49
Q

What is the fundamental heredity unit? why?

A

DNA as it directs all processes in a cell
Reproduction is dependent upon DNA replication
Replication ensures that important information is transferred down the generations

50
Q

Why is DNA replication important?

A
  • Reproduction of cells is dependent upon DNA replication, as the creation of new cells requires more DNA to be produced
  • By copying the genetic material of a cell, replication ensures that information important for life is transferred down through the generations
  • If DNA were not replicated before mitosis and meiosis, cell division would have the amount of DNA, and resulting cells would die due to inadequate amounts of genetic information
  • DNA replication is a high-fidelity process, ensuring that daughter DNA strands carry the same gene, and encoding all the essential proteins for life.
51
Q

why is mitosis essential?

A

Mitosis is essential for the development and growth of organisms. Mitosis increases the number of cells in an organism, allowing for the development of multicellular bodies.
Mitosis also allows for old cells to be replaced, ensuring that tissues continue to function effectively and efficiently.

52
Q

what is mitosis’ importance in reproduction?

A

For organisms like humans, mitosis allows us to develop maturity when we. And pass our genetic information onto offspring through sexual reproduction.
- Some organisms reproduce by asexual reproduction, which is facilitated by mitosis. In these cases, mitosis creates the next generation of molecules

53
Q

What is the end product of meiosis?

A

gametes

54
Q

How does meiosis increase variation? why is this important?

A

meiosis purposefully introduces variation. Processes of crossing over, independent assortment and random segregation allow for combinations of different alleles, increasing variation in offspring and the wider population.

Genetic diversity (introduced by meiosis and sexual reproduction) is very important for the continuity of species, as mutation and variation are essential factors for survival and evolution.

55
Q

Does mitosis or meiosis purposely increase variation?

A

meiosis

56
Q

what is nRNA?

A

The intermediary molecule called mRNA transmits information out of the nucleus for processing. mRNA is a messenger ribonucleic acid. It is chemically quite similar to DNA, except that it is a single-stranded, contains a ribose sugar instead of a deoxyribose sugar, and instead of thymine (T) nitrogenous base, it has uracil (U) in its place.

57
Q

steps involved in transcription:

A
  1. RNA polymerase binds to the promoter sequence upstream up from a gene.
  2. As RNA polymerase moves along the DNA strand, a small region of DNA is unwound
  3. RNA polymerase ‘reads’ the DNA template strand, matching complementary free-floating nucleotides (NTPs) to create a chain containing the same coding information.
  4. A mRNA molecule is sequentially synthesised by RNA polymerase, as it continues to move along the DNA strand
  5. Terminator sequences end the transcription of DNA, and the newly formed mRNA molecule is released.
58
Q

steps involved in translation:

A
  1. mRNA docks to the ribosome
  2. The ribosome matches a complementary tRNA molecule to the mRNA by matching codon/anticodon sequences.
  3. As subsequent tRNA molecules dock, a polypeptide bond is formed between the adjacent amino acid molecules which they carry.
  4. As the mRNA molecule continues to be read, the polypeptide chain is elongated by continued addition of amino acids
  5. The polypeptide fold and undergoes post-translational modifications, resulting in a mature protein ready for use in
  6. the cell.
59
Q

what is involved in translation?

A

The genetic sequence of the mRNA molecule is ‘read’ by ribosomes. This code is translated into groups of three nucleotides called a codon.

60
Q

What is translation and what is transcription?

A

Transcription is literally ‘copying’, you’re using the same basic units (nucleotides) to create an intermediary molecule (RNA)
Translation is actually changing the language. We are turning information stored as nucleotide sequences into amino acid sequences

61
Q

What is the order of processes in creating proteins?

A

DNA replication
DNA transcription to mRNA
mRNA translates to form proteins

62
Q

What is the importance of mRNA?

A

Conveys genetic material in DNA to the ribosome

  • during translation, each triplet of bases (codon) is used to identify the appropriate anticodon
  • mRNA sequence must therefore be accurate for the correct polypeptide to be produced at the ribosome and therefore to maintain healthy cell function
  • Hence mRNA is of critical importance in both transcription and translation
63
Q

tRNA- what does the t stand for?

A

transfer

64
Q

what is the importance of tRNA?

A

tRNA is responsible for decoding the mRNA as it threads through the ribosome, using the mRNA codon during translation. The corresponding tRNA carries a complementary anticodon which codes for a specific amino acid.

  • As the tRNA decodes the mRNA molecule, a chain of amino acids is formed via peptide bonds, which then forms a polypeptide
  • Hence, the tRNA molecule is extremely important, as it decodes the mRNA molecule and supplies the appropriate amino acid so that ultimately the correct polypeptide & protein can be formed to maintain cell function.
65
Q

What did Gregor Mendel do for genetics?

A

In the 1860’s Mendel formulated the principles of genetics by experimentation with garden peas.
He stated that factors were weaker or stronger not dominant or recessive

66
Q

What are monohybrid crosses?

A

Involves one factor only

F2 generation 3:1

67
Q

Homozygous vs Heterozygous genotypes:

A

Factors that are the same= homozygous
Factors that are different = heterozygous
In the heterozygous condition, the factor that is fully expressed is termed dominant. The recessive factor is masked by the dominant factor.

68
Q

What is the difference between an allele and a gene?

A

An allele is an alternative form of a particular inheritable characteristic e.g. brown or green
A gene is a section of DNA coding for proteins that expresses itself as the phenotypes of an organism. E.g. eye colour.

69
Q

Phenotype vs genotype:

A

Phenotype is the outward appearance of an organism

Genotype is the actual alleles that are present on the chromosomes of the organism.

70
Q

When do Mendellian ratios not apply?

A

Sex-linked genes and co-dominant genes do not display the phenotype ratios predicted by Mendel’s laws.

71
Q

How are the 23 chromosomes divided in terms of roles?

A

22 pairs of autosomes and 1 pair of sex chromosomes in humans

72
Q

What do sex chromosome do?

A

Sex chromosomes carry genes that determine the sexual characteristics of a person and influence whether they are male or female

73
Q

Females chromosomes

A

Females = XX (homogametic)

74
Q

Male Chromosomes

A

Males = XY (heterogametic)

75
Q

What chance do offspring have of being male or female?

A

50/50

76
Q

Why do sex linkage characteristics occur?

A

The X chromosome is larger and may also carry genes for non-sexual body characteristics. These are sex-linked genes as they are physically linked to the sex chromosomes
Females are often carriers, meaning males are more likely to be affected by sex-linkage

77
Q

What is co-dominance?

A

If an individual is heterozygous for a characteristic there are some cases where both alleles are expressed in the phenotype.
Both alleles are labelled with upper case letters

78
Q

What is incomplete dominance?

A

In incomplete dominance, a heterozygous individual blends the two traits
We can still use the mendelian model to predict the results of crosses for alleles that show incomplete dominance

79
Q

What is fertilisation and how does it create variation?

A

Gametes meeting and combining to form a zygote. When 1 gamete from each parent combines it results in recombination and independent assortment in meiosis, this produces a unique set of DNA.

80
Q

What is a mutation and how does it create variation?

A

An alteration in the nucleotide sequence of the genome of an organism or DNA. They can introduce new alleles into a population and increase variation.

81
Q

What is crossing over?

A

arms of homologous chromosomes exchange material during metaphase.

82
Q

How does crossing over create variation?

A

The exchange of genetic material causes the mixing of paternal and maternal genes and results in an increased combination of genes that may be transmitted by gametes to offspring

Biology HSC 2021 (3 decks)

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