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genetics (for mr d) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

chromosomes

A
  • contains a single DNA molecule ( will carry a number of genes) and is associated with proteins
  • constantly change appearance during life
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2
Q

structure of chromosome

A
  • extremely long but still able to fit into the nucleus
  • DNA is tightly packed into chromosomes
  • DNA wraps around a histone, and a nucleosome is formed.
  • important in packaging DNA efficiently and protecting it
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3
Q

structure of chromosome (eukaryotic)

A
  • DNA coiled around small proteins known as histones.
    • consist of about twice as much protein as DNA.
  • before dividing, chromosomes become very condensed. (Prophase: Chromatin)
  • nucleosomes fold in a way to produce supercoils
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4
Q

4 types of chromosomes

A
  • metacentric: centromere position in the centre, arms are equal length
  • submetacentric: centromere positioned towards one end, arms are uneven length, q arms = 2x length of p arms
  • acrocentric: centromere is very close to one end, q arms and very short p arms
  • telocentric: centromere at very tip of arms, no p arm visible. not present in humans
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4
Q

centromere

A

a constriction point which divides the chromosome into two sections

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5
Q

chromosome size

A
  • each DNA molecule contains a number of genes
    • code for 40 proteins each
    • maybe present to keep genes apart so that enzymes and other molecules can easily interact with them
  • chromosomes differ in size because of differences in no. of genes and amount of spacer DNA between genes
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6
Q

spacer DNA

A

genes on a DNA molecule are separated by regions called spacer DNA
- no function

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7
Q

locus/loci

A

each gene has a particular position, known as locus, on a specific chromosome

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8
Q

ploidy

A

no. of chromosome sets a cell carries

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9
Q

Haploid (n)

A

cells that contain only one set of chromosomes (e.g. gametes) (23)

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10
Q

Diploid (2n)

A
  • cells that contain two sets of chromosomes; one set from each parent (e.g. somatic cells) (46)
  • diploid no. of chromosomes of organisms varies widely
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11
Q

Homologous Chromosomes

A
  • identical pairs of chromosomes
  • carry the same genes, but not necessarily the same versions of those genes
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12
Q

Sex chromosomes (allosomes)

A
  • sex determination in different organisms varies.
  • in humans (and some other organisms) a special pair of chromosomes, determine the sex of the individual
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13
Q

heterogametic

A

individuals with different sex chromosomes

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14
Q

homogametic

A

individuals with two similar sex chromosomes

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15
Q

genes

A
  • segments of DNA that code for a protein and can be made up of a small number of bases or a large number of bases.
  • determine the inherited characteristics of organisms
  • found on chromosomes
  • made of unique sequences of DNA
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16
Q

alleles

A

alleles are different versions of the same gene.

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17
Q

karyotypes

A
  • whole 46-chromosome set containing 23 pairs
  • specifically shows an individual set of genetic information
  • metaphase 1
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18
Q

somatic cells

A

all cells in the body of an organism apart from sex cells (gametes)
e.g skin cells, muscle cells

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19
Q

gametes

A
  • specialised sex cells that combine in sexual reproduction
  • formed by a type of cell division called meiosis
  • this occurs in specialised reproductive organs (gonads)
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20
Q

meiosis

A
  • only occurs in eukaryotes and in gonads
  • allows for genetic variability vis genetic recombination and crossing over
  • is a reduction division resulting in 4 haploid daughter cells unidentical to each other
  • each daughter cell ends up with only half of the chromosomes the parent cell had
  • 1 chromosome (2 chromatids) from each pair of chromosomes.
  • after meiosis 2 there is still 1 chromosome but with a single chromatid
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21
Q

Meiotic Genetic Recombination (Crossing Over)

A
  • occurs during meiosis as the alleles are rearranged between the four chromosomes in the starting pairs
  • Prophase I
  • creates daughter cells that are genetically unique
  • new set of combined chromosomes are called a tetrad
  • genes from non-sister chromatids are swapped to create gametes containing new and unique chromosomes that neither parent has
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22
Q

Genetic Variation in Sexual Reproduction

A
  • an independent assortment of homologous chromosomes during Metaphase 1
  • How homologous chromosomes line up next to each other (which one is on the left and which is on the right) is completely random
    • so the combination of chromosomes that end up in a gamete is also random
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23
Q

meiotic cell division

A

Interphase- before meiosis occurs DNA is replicated, and chromosomes duplicate, result in two identical sister chromatids
P1- condense, plump and visible, crossing over occurs, nuclear envelope disappears, spindle fibres begin to form
M1- line up in the middle (equator), arranged independently (indep assortment), spindle fibres attach to each centromere
A1- spindles shorten and pull the chroms apart, reducing no. of chroms (reduction division)
T1- Cleavage furrow is formed, chromosomes decondense, 2 haploid daughter cells nuclei
P2- nuclear envelope breaks down again, SPINDLE FIBRES ARE RECREATED
M2- duplicated chroms line up in middle, spindle fibres attach to centromere
A2 spindles shorten separating sister chromatids
T2 cleavage furrow formed, chromosomes decondense, 4 haploid daughter cells

24
Q

stained karyotypes

A
  • chromosomes are stained, which shows up characteristic patterns of light and dark bands
  • known as G-bands
  • reflect differencesn the amounts of A & T bases and G & C bases
  • banding patterns are specific and consistent
  • can be used to distinguish between chromosomes
  • can be used to look for subtle changes in chromosomes structure that may be associated with genetic abnormalities
25
Q

duplication, inversion, translocation

A
  • occurs when one extra but identical piece of a chromosome is copied and added to the chromosome
  • occurs when one piece of a chromosome is broken up, turned upside down, and reattached, inverting the genetic material
  • caused by the rearrangement of parts of non-homologous chromosomes
26
Q

Genotype

A
  • unique sequence of DNA
  • two alleles a person has inherited for a particular gene
  • set of alleles that an organism has inherited
27
Q

Phenotype

A
  • The individual’s observable traits
  • A persons phenotype is made up of their genetics (genotype) and environmental factors
28
Q

trisomy 21

A

down syndrome

29
Q

turner syndrome

A

diagnosed when a female only carries one X chromosomes

30
Q

klinefelter syndrome

A

diagnosed when a male carries two X chromosomes and a Y chromosomed

31
Q

deletion/deficiency

A

loss of a chromosome segment

32
Q

DNA

A
  • molecules called nucleotides
    • are the building blocks of DNA
    • individual lines that are sequences together linearly to create a strand of DNA
32
Q

nucleotide atomic structure

A
  • a phosphate group
  • a five-carbon (pentose) sugar
  • a nitrogenous base
32
Q

nucleotides

A
  • DNA is a large macromolecule (large number of atoms)
  • contain a phosphate molecule and a deoxyribose sugar which are bound together
  • creates the sugar-phosphate backbone
  • candy cane-like structure
32
Q

complementary base pairs

A

DNA: AT GC
RNA: AU GC

33
Q

2 Types of Nitrogenous Base Structures

A
  • Purines: (Remember: Pure = Angels and Goodness) which is the Double ring structure
  • Pyramidines: (Remember: Pyramids = Tools & Cements) which is the Single ring structure
34
Q

DNA HELIX

A
  • the way the nucleotides are joined results in a double-stranded DNA molecule known as a double helix
  • given the base sequence of one strand, we can determine the sequence of the other because of this base-pair rule
  • the two strands of DNA (held together via hydrogen bonds) are said to be antiparallel. One stand is 5’ → 3’ and the other is 3’ → 5’ (’ = Prime)
35
Q

Homozygous and Heterozygous Alleles

A

Homozygous: the alleles in a genotype are identical
Heterozygous: the alleles in a genotype are different

36
Q

Dominant and Recessive Traits

A
  • a trait is dominant if at least one allele for the trait is present
  • a trait is recessive if two copies of the allele for the trait are required for the trait to be expressed
37
Q

Incomplete Dominance:

A

when heterozygotic organisms’ traits blend alleles to become hybrids

38
Q

co-dominance

A
  • both alleles are equally expressed
  • are both dominant alleles and neither masks the other
  • both genetic traits are found in these organisms
39
Q

Mendel’s second law

A

states that the alleles of a gene controlling one trait assort independently of alleles of another gene controlling a different trait

40
Q

Complete dominance

A

the dominant allele completely masks the effect of the recessive allele in heterozygous conditions.

41
Q

environmental factors infleunce on phenotype

A
  • organism’s environmental factors have a significant effect on their phenotype
  • changes to phenotype due to environment are common amongst animal and plant organisms
42
Q

epigenetics

A

different phenotypes that are caused by changes in gene expression rather than genetic code changes

42
Q

neg. consequences of epigenetics

A
  • E.g. Cancer suppressing genes can be switched off
  • found on DNA histone proteins
  • switch on/off specific genes
43
Q

reprogramming

A

during the formation of gametes during meiosis epigenetic tags are usually erased to ensure the health of the growing embryo

43
Q

Mendel’s principle of segregation

A

states that individuals carry pairs of alleles of each gene, which segregate into gametes during meiosis so that each gamete carries one allele of each gene

44
Q

purpose of test crosses

A
  • find out how many genes control the phenotype
  • To determine if an individual showing the dominant pheno is a heterozygote or homozygote
45
Q

monohybrid crosses

A

a cross between two individuals involving a single gene

46
Q

pure-breeding organisms

A

homozygous in relation to the gene of interest and produce genetically identical offspring

47
Q

Autosomal Incomplete Dominance

A
  • we see incomplete dominance because the allele controls the production of an enzyme that regulates the development of the red pigment
    • thus, with some functional enzyme, the colours blend
48
Q

autosomal co-dominance

A
  • alleles for coat colour are inherited
  • Heterozygotes have both red and white coats, called “Roan”
49
Q

carriers

A

heterozygous females are carriers because they are able to pass on the recessive allele, but don’t express the trait themselves

50
Q

pedigrees

A
  • can be used to follow the inheritance of traits through a family over a number of generations
51
Q

dihybrid cross

A
  • a cross of two independently assorted traits
  • multiple phenotypes possible
  • two alleles for each gene (trait)
  • involving two gene loci
52
Q

gene linkage

A
  • the tendency for two or more genes on the same chromosomes to be inherited together
  • the closer two genes are on a chromosome, the greater the likelihood that they will be inherited together
  • never 100% due to crossing over (recombination), which occurs between non-sister chromatids of homologous chromosomes during meiosis
53
Q

chiasma

A

the point where homologous chromosomes join during crossing over

Biology (8 decks)

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