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Biology > Topic 3 Voice of the genome > Flashcards

Topic 3 Voice of the genome Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Describe how DNA is organised in a bacterial cell. (3)

A

-DNA is circular.
-DNA not associated with histone proteins.
-Several plasmids.
-Located in cytoplasm/no nucleus.

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2
Q

What’s the differences between eukaryotic and prokaryotic cells? (4)

A

-Eukaryotic cells have membrane bound organelles.
-Eukaryotic cells contains RER.
-Eukaryotic cells have 80s ribosomes whereas prokaryotic cells have 70s ribosomes.
-Eukaryotic cells have linear DNA.
-Eukaryotes don’t have plasmids.

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3
Q

Describe features that could be used to identify prokaryotic cells in blood sample. (4)

A

-Presence of cell wall.
-Circular DNA/plasmids.
-70s ribosomes.
-Pilli/flagellum.
-Capsule/mesosome.

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4
Q

Explain why the nucleus cant be seen at the end of prophase. (2)

A

-As nuclear membrane is broken down.
-As DNA is condensed into individual chromosomes.

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5
Q

Describe how a polypeptide is processed to produce a protein. (4)

A

-The polypeptide chain moves through the endoplasmic reticulum then the Golgi apparatus.
-In the RER the polypeptide is folded.
-In the Golgi apparatus a carbohydrate is added.
-The protein is then transported around cell in vesicle.

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6
Q

Explain why interferon made by genetically modified bacteria is different from interferon made by animal cells. (3)

A

-Bacteria doesn’t have an RER.
-Meaning polypeptide chain isn’t modified properly.
-Therefore protein is incorrectly folded.

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7
Q

Describe what happens in an acrosome reaction. (1)

A

-Sperm cell releases digestive enzymes that digest zona pellucida.

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8
Q

Devise an investigation to determine the effect of exposure time to Agil on the rate of mitosis in onion root tips. (6)

A

-Controlled concentration of agil used.
-Temp/age of onion kept same.
-Roots exposed to agil for a range of time intervals.
-HCl used to make cells more visible, macerate.
-Toluidine blue stain used to make chromosomes more visible then squash down with a cover slip.
-Observe under microscope and count no. cells undergoing mitosis and total no. cells and calculate mitotic index.

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9
Q

Explain why HCl is added to root tip in mitosis CPAC. (2)

A

-Breaks down middle lamella.
-Allowing cells to be separated.
-So light can pass through more easily.

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10
Q

Explain why a stain is added to root tip in mitosis CPAC. (2)

A

-Makes chromosomes more visible.
-So stages of mitosis can be identified.

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11
Q

Explain how preventing shortening of spindle fibres affects mitosis. (2)

A

-Sister chromatids can’t be separated.
-Mitosis stops at metaphase.
-Daughter cells produced with incorrect no. chromosomes.

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12
Q

Describe the events of fertilisations that occurs after the acrosome reaction. (3)

A

-Sperm cell fuses with egg cell membrane.
-Cortical granules release contents into zona pellucida.
-Contents of cortical granules cause zona pellucida to harden once they react with one another.
-Sperm and egg cells haploid nuclei fuse.

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13
Q

Explain why twins may be genetically different although they have the same parents. (2)

A

-Each zygote is formed from different gametes.
-Each gamete contains different combinations of alleles.
-Different combinations of alleles due to independent assortment and crossing over during meiosis.

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14
Q

Once a egg cell has been fertilised by a sperm cell explain why a second sperm cell can’t fertilise the same egg cell. (3)

A

-Cortical reaction occurs meaning cortical granules fuse with egg cell membrane.
-Causing the zona pellucida to harden.
-Therefore other sperm cells can’t reach egg cells membrane.

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15
Q

Explain what is meant by the term sex linked disorder. (2)

A

-It is a disorder caused by a mutated allele.
-Located on sex chromosomes (X/Y).
-So disorder is more likely linked in one gender than the other.

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16
Q

Explain why a sperm cell with 2 flagella may reduce fertility. (3)

A

-Presence of 2 flagella affects ability of sperm to propel itself.
-May prevent sperm from reaching egg.
-Preventing fertilisation.

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17
Q

Describe how meiosis leads to genetic variation in gametes produced. (2)

A

-Non identical gametes produced due to independent assortment of chromosomes.
-Crossing over between non sister chromatids of homologous chromosomes.

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18
Q

Explain why some genes show linkage and others show sex linkage. (3)

A

-There are more genes than there are chromosomes.
-Linkage relates to genes for different characteristics located in same non sex chromosomes.
-Sex linkage relates to genes on sex (X/Y) chromosomes.

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19
Q

Explain how crossing over may differ in sex chromosomes. (2)

A

-Crossovers can’t form between some sections of X and Y chromosomes.
-As they aren’t homologous chromosomes.

20
Q

What is a homologous pair?

A

2 Chromosomes with exactly the same genes but different alleles, maternal and paternal.

21
Q

Explain why is DNA replicated before mitosis begins. (2)

A

-To ensure there’s one copy of each chromosome in each daughter cell.
-To ensure daughter cells are genetically identical.

22
Q

Name the part of a chromosome that is occupied by a gene. (1)

A

-Locus.

23
Q

Describe what happens during prophase in an animal cell. (3)

A

-Nucleus/nuclear envelope breaks down.
-Spindle fibres formed.
-Chromosomes condense.
-Centrioles migrate to opposite poles/ends of the cell.

24
Q

Why is there a high density of mitochondria in the midpiece of a sperm cell? (1)

A

-Provides energy for movement of the flagellum.

25
Q

Explain why genes found on sex chromosome pair have a pattern of inheritance that is different from genes found on other chromosome pairs. (2)

A

-X chromosome carries genes that aren’t present on Y chromosome.
-Males have only one copy of some genes.
-If only one allele inherited it will be expressed.

26
Q

Describe the appearance of chromosomes in cells undergoing metaphase. (2)

A

-Chromosomes are condensed.
-They are joined to spindle fibres.
-The chromosomes are aligned on the equator of the cell.

27
Q

What does polygenic mean? (2)

A

-A characteristic showing continuous variation.
-Caused by multiple genes at different loci.

28
Q

What is continuous variation?

A

Variation within a range, includes mass and height.

29
Q

What is discontinuous variation?

A

Can only take particular values such as gender or shoe size.

30
Q

Explain how epigenetic changes affect development of tissues in embryos. (3)

A

-DNA is wrapped around histones.
-Acetylation/modification of histone affects binding of RNA polymerase.
-Methylation of DNA affects transcription of genes.
-Therefore gene expression is altered.
-

31
Q

Give a difference between a tissue and an organ. (1)

A

-A tissue is made of one type of cell and an organ is made of different tissues.

32
Q

Describe the decisions society has to make about the use of embryonic stem cells. (3)

A

-Embryonic stem cells are totipotent and can be used in a wider range of therapies than other stem cells.
-Source of embryonic stem cells has to be regulated.
-Ethical issues surrounding the embryos being destroyed by using embryonic stem cells.
-Need for research establishments to be regulated/licensed.

33
Q

Give the meaning of the term totipotent cell. (2)

A

-A cell that has the ability to differentiate.
-Into all types of cells.

34
Q

Describe how embryonic stem cells can be specialised to form tissues and organs. (3)

A

-Chemical signals/activators and repressors cause some genes to be switched on or off.
-The genes that are activated/switched on are transcribed and produce mRNA.
-mRNA leads to synthesis of specific proteins which cause cell modification.

35
Q

Explain why stem cells from the heart can’t be used to grow cells to repair the cornea. (3)

A

-Stem cells from the heart are not totipotent.
-Therefore some genes have already been activated and deactivated.
-Therefore will not be able to specialise into cornea cells.

36
Q

Explain why chemicals from the eye are needed to produce corneal cells from stem cells. (4)

A

-Chemicals cause some genes to be switched on or off.
-The genes that are switched on are transcribed producing specific mRNA.
-Specific mRNA is translated into specific protein.
-These proteins cause the cell to develop into a corneal cell.

37
Q

Deduce why age affects time taken to recover from injuries. (3)

A

-As age increases, time taken to recover from injury increases.
-Due to fewer stem cells in bone marrow with age.
-Fewer stem cells to replace cells in bone/muscle/cartilage tissues.

38
Q

What is a stem cell? (2)

A

-A cell that is undifferentiated.
-That can give rise to specialised cells.
-That can divide to produce more stem cells.

39
Q

Compare and contrast the results of mitosis and meiosis in production of sperm and stem cells. (4)

A

-They both increase the number of cells.

-Mitosis produces diploid cells and meiosis produces haploid cells.
-Mitosis produces cells that are genetically identical , whereas meiosis produces cells that are genetically different.
-Mitosis results in 2 daughter cells whereas meiosis results in 4 daughter cells.

40
Q

Epigenetic changes can cause monozygotic twins to have different body masses.

Explain how epigenetic changes can cause differences in a characteristic. (3)

A

-DNA methylation/histone modification.
-Causes genes to be switched on or off/activated or deactivated.
-Affecting enzyme production.

41
Q

Explain how epigenetic changes affect activation of genes in daughter cells. (3)

A

-Genes switched on or off in stem cells.
-Due to DNA methylation.
-Therefore same genes will be activated in daughter cells.

42
Q

Explain why an individual may have a greater adult height than their biological parents. (4)

A

-Height is affected by environment as well as genotype.
-Height is an example of polygenic inheritance.
-Therefore offspring can inherit a mixture of alleles from both parents.
-Diet can also influence height, high calcium or protein diet can increase height.

43
Q

Describe how stem cells can give rise to different types of cells. (4)

A

-Different stimuli activate/switch on different genes.
-The activated genes are transcribed to produce mRNA.
-mRNA then translated to produce a protein.
-Protein determines function of cell.
-Different proteins produced from different activated genes produce different types cells.

44
Q

Describe what is meant by the term operon. (2)

A

-A section of DNA.
-Controlled by a single operator/promotor.

45
Q

Describe the effect of lactose on the lac operon. (3)

A

-When lactose is present it binds to the repressor.
-This changes the repressors shape, now it can’t bind to the operator site.
-This allows RNA polymerase to now carry out transcription.

Biology (9 decks)

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