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bio unit 2 > 7A- genes and chromosomes > Flashcards

7A- genes and chromosomes Flashcards

• the distinction between genes, alleles, and a genome • the nature of a pair of homologous chromosomes carrying the same gene loci and the distinction between autosomes and sex chromosomes • variability of chromosomes in terms of size and number in different organisms • karyotypes as a visual representation that can be used to identify chromosome abnormalities

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Biology 101 flashcards
1
Q

deoxyribonucleic acid DNA

A

a double-stranded nucleic acid chain made up of nucleotides. DNA carries the instructions for proteins which are required for cell and organism survival

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2
Q

nucleic acid

A

the class of macromolecules that include DNA and RNA. all nucleic acids are polymers made out of nucleotide monomers

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3
Q

nucleotide

A

the monomer unit of nucleic acids. Made up of a nitrogen-containing base, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a phosphate group

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4
Q

gene

A

a section of DNA that carries the code to make a protein

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5
Q

genome

A

the complete set of DNA contained with an organism’s chromosomes

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6
Q

allele

A

alternate forms of a gene

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7
Q

locus (pl. loci)

A

the fixed position on a chromosome where a particular gene is located

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8
Q

inheritance

A

the genetic transmission of traits from parent to offspring

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9
Q

phenotype

A

the observable trait of an individual

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10
Q

haploid

A

describes a single set of chromosomes (n)

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11
Q

histone protein

A

highly basic proteins that associate with DNA inside the nucleus and help it condense into a chromosome allowing it to fit inside the nucleus

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12
Q

chromosome

A

the structure made of protein and nucleic acids that carries genetic information

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13
Q

somatic cell

A

any cell that is not a reproductive cell (such as sperm and egg cells). Somatic cells are diploid (2n), meaning they contain two sets of chromosomes – one inherited from each parent

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14
Q

chromatid

A

one half of a replicated chromosome. Prior to cell division, chromosomes are duplicated and two copies join together at their centromeres (joined chromatids are known as sister chromatids)

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15
Q

homologous chromosomes

A

a pair of chromosomes of similar length, gene position, and centromere location. One of the pair is inherited from the mother (maternal chromosome) and the other from the father (paternal chromosome)

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16
Q

homologue

A

a homologous chromosome

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17
Q

karyotype

A

a visual representation of an individuals entire genome organised into homologous pairs

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18
Q

autosome

A

any chromosome (1-22) in humans that isn’t a sex chromosome

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19
Q

sex chromosome

A

a chromosome responsible for determining the biological sex of an organism. in humans sex chromosomes can either be an x or a y

20
Q

aneuploidy

A

when a cell or organism varies in the usual number of chromosomes in its genome by the addition or loss of a chromosome

21
Q

polyploidy

A

when an organism contains additional sets of chromosomes in its genome

22
Q

monosomy

A

a genetic abnormality where an organism has one missing chromosome

23
Q

trisomy

A

a genetic abnormality when an organism has one extra chromosome

24
Q

tetrasomy

A

a genetic abnormality where an organism has 2 extra chromosomes

25
Q

what is a nucleotide composed of?

A

a phosphate group
a deoxyribose sugar
a nitrogenous base which can be one of four varieties (adenine, thymine, guanine, cytosine)

26
Q

distinguish between a genome, gene and an allele

A

A genome is the haploid set of chromosomes within an organism, including all of its genes. A copy of the entire genome is contained in all cells within the body that have a nucleus.
A gene is a section of DNA that carries the code to make a protein. our genes are what form the basis of inheritance, and can be found at specific locations on our chromosomes (gene loci)
An allele is an alternative form of a gene. We typically have two alleles one from each parent which are found at teh same gene locus on corresponding chromosomes

27
Q

what do genes act as?

A

they act like a set of instructions which a cell will read to then create the important protein molecules needed for a range of cellular functions like growth and regeneration. the order of bases in the double helix determines which protein is made

28
Q

how many different genes are inside each of your cells?

A

25000

29
Q

how are chromosomes arranged?

A

they are arranged into homologous pairs based on the specific genes they possess

30
Q

structure of a chromosome

A

telomeres at the top
short arm
DNA that runs through the arms that is coiled tightly around histone proteins to be packaged
centromere
long arm
sister chromatids

31
Q

function of telomeres

A

A region of repetitive base sequences that is found at the end of every chromosome. It is used to protect the ends of chromosomes from fusing with other nearby chromosomes in the nucleus.

32
Q

function of DNA molecules

A

Each chromosome is composed of a long DNA molecule that has been coiled tightly around histone proteins.

33
Q

function of the centromere

A

A specialised sequence of DNA that holds together the two chromatids. It is very
important for the process of meiosis.

34
Q

function of sister chromatids

A

The identical daughter strands of a replicated chromosome.

35
Q

function of the short arm

A

Also known as the ‘p arm’ – this is the section of the chromosome that is shorter in length.

36
Q

function of the long arm

A

Also known as the ‘q arm’ – this is the section of the chromosome that is longer in length.

37
Q

what are the criteria for homologous chromosomes?

A

1 they are the same in size and length
2 they have the same centromere position
3 they share the same genes at the same gene loci.

38
Q

what do karyotypes/karyograms show?

A

they display structural features and are used to check for possible genetic abnormalities. when reading karyotypes, scientists check that there are the correct number of chromosomes present and that the size and length are correct.

39
Q

how are karyotypes organised?

A

homologous pairs are arranged according to size
pairs labelled 1-22 are known as autosomes, each containing the genetic info for thousands of genes
sex chromosomes determine the gender of an organism- XX is female and XY is male

40
Q

what is the diploid chromosome number in human somatic cells

A

2n=47

41
Q

what is a diploid number of another species?

A

cat- 2n=78
butterfly- 2n=190
corn- 2n=20
coconut tree- 2n=32

42
Q

what is a type of monosomy?

A

• Name: Turner syndrome
• Mutation: single X chromosome (often presented as XO)
• Incidence rate: 1 : 2 000
• Common symptoms: infertility, short stature, fused neck and head

43
Q

what is a type of trisomy?
(down syndrome)

A

• Name: Down syndrome (otherwise known as trisomy 21)
• Mutation: extra copy of chromosome 21
• Incidence rate: 1 : 1 000
• Common symptoms: delayed physical growth, possible heart defects, flattened facial profile, mild to moderate intellectual disability

44
Q

what is another type of trisomy?
(Klinefelter syndrome)

A

• Name: Klinefelter syndrome
• Mutation: extra X chromosome in males (XXY)
• Incidence rate: 1 : 650 males born
• Common symptoms: accelerated growth and taller height, small testes and reduced testosterone levels, delayed or incomplete puberty, decreased muscle mass, learning and intellectual disabilities, infertility

45
Q

what is a type of tetrasomy?

A

• Name: Tetrasomy X (otherwise known as XXXX)
• Mutation: two extra copies of the X chromosome
(totalling 4)
• Incidence rate: there exists a community of around 100–150 confirmed cases worldwide. However, because females with the disorder rarely show symptoms, it is possible that a large majority of tetrasomy X cases go undiagnosed.
• Common symptoms: mild delay in physical development, delayed speech development, slight to moderate learning difficulties

46
Q

what is polyploidy?

A

a chromosomal abnormality in which an organism has more than two sets of each chromosome meaning instead of a human being 2n=46 they would be 3n=72
it is typically lethal in humans, meaning it is rare for a foetus to survive to term. but it is common in other organisms such as plants to thrive with additional sets of chromosomes- increasing size and hardiness in some fruits or animals like farmed Atlantic salmon (which are now sterile and grow faster)

bio unit 2 (7 decks)

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