Biology: patterns of inheritance

what is a chromosmes

the DNA stirage molecule that is made up of 2 sister chromatide bound togther when replicated

• telomereas are found at their ends

• sister chromatids are indentical

Karyotype

a viual representtaion of of ones chromosomsal make up with erveything sorted into pairs which ecah chromosme in the pair coming fro eah parnet

Diploid cells vs haploid cells

Diploid cells: cells with 2 copies of the same chromosome with one comming from ecah parent

• 2 set f chromsomes with 1 chromosme have 2 sister chromatids make a homologous pair

haploid cell: cell with onyl 1 copy of each chromosome that comes from one of that person's parents

non-sister chromatids

are euqivilante /aprt of a homologous pair but come from differnt sourse

• one is a sister chromatide from the mother and the other is teh sister chromatid from te father

Homologous pair

a pair of matching chromosmes that contain the same genes but often differnt allel or are from differnt aprnets

Gametes

haplois reproductive cells that are produced from germline cells in meiosis

• combine in reproduction to creat a diploid zygote that become an offspring

Mitosis ( movement of chromosomes)

1. chromosomes replicate in the s pahse so that they conatin 2 ssietr chromatids

2. the chromatids then sperate so that they are in two differnt cells

meiosis overveiw

meiosis 1: the hmologous pairs bind togther and are then segragated into two seprate cells

• ceel created will hve two chromosoems that are not part of a homologous pair

• 1 pair = 2 sister hromtid sets from ecah parent

meiosis 2 : the sister chromtids from teh chromsomes then sperae into 2 cells each creating haploid gametes

• 1 copy of 1 chormosome

what is crossing over in meiosis

the process at which the genetica material in non-sister chroatid of homologous pair cross over and are swapped casing geentci variation

• rare as only 1-3 of the 23 chromosomes will cross over in meiosis

• also called recombination

Mieosis 1 propahse: recombination

1. nonsister chromatids are held togther at the centromere and apur up in homologpus pairs

2. two chiasm form on the top and bottom of the chromosome which are the point at which the chromosome will bareak and rejoin casuing them to swap genetic material

• no longer held togther at the centromere

Meiosis 1 anaphase - recombination

1. the cchomosmes that have then crossed over will wlign in the middle of the cel in metaphase

2. they will they be separet to ecah side of th cell int two suster chromatids

anapahse of meiosis 2 - recombination

the sister chramotids will then become chromsomes as then enter the gametes with some of then just having one parenst DNA and the other having a combination on just one chromosme

what is independent assortment

another process that can caused genetic varition in gametes at which the differentaition of inheritance is due to the way sister chromatids are align in the cneter during metapahse

• theree are two possibel arranges ments: chromotides are alternate ( the first pair in mother fater and the secound in father mother) or the look the same ( Mother father, mother father)

• 1 cell going through meiosis has 1 possible outcome but hundred will have 2 possible outcomes

out comes of independent assortment

in the alternating possibility the gametes produced will have 1 chromosmes from the maother and one chromsme from the father ( soecifically from the two chormosmes mentioned)

in the same order possibilty ecah gamete will have 2 chromsomes from the same parent

Mutations in Meiosis

Mutaions can also cause genetic veriation with erreors in the duplication of DNA leading to the possibility of inheriting certain disorder and mutation

• can create differnt version of the same gene

Non-disjunction

when chromsomes do not undergo meiosis properly leading to the xcreation of gamete with abnormal numbers of chromosmes that can have detrimental effects on offspring

• can occur in both meiosis 1 or 2

trisomy vs monosomy

Trisomy: a gamete 2 copies of the same chromsomes comming from bith parants ( hence an extra chromosome)

Monosomy: a gamete with no copies of a chromsome from either parent ( missing a chromosomes)

Non-disjunction in Meiosis 1

when the homologous pair do not sperate properly meaning they bith end up in 1 cell after separation instead of being spilt between 2 cells

• casuses 1 cell to have 23 chromsomes and the other to have only 22

• the gamete produced by the 1st cell would be trisomy and the 2nd cell would be monsomy

Non-disjunction in meiosis 2

a process at which the sisterchromtids do not separate properly

• causing both chromosomes to end up in 1 gamete while the other gamete has no copy of the chromosome

Trisomy 21 ( down syndrome)

a reslt of nondijusctio occuring at chromosme 21 leading to the formation of down syndrome

• an aneuploidy condition which is condition due to an abnormal number fo chromomseom

Heredity

the transfernec of certain traits in the form og genes from parent to child

symbols in pedigree tables meaning

• circle = female

• squres = males

• diamond = unknown ( pregnancy / future child)

• bank = unaffect

• fliied in = affect

• dot = carrier

• 1 line across = mating

• 2 line across = mating but related

• line down to more people indicates a parent-child relationship

• one across line going start down at end = sibling relation

• a triangle connect two = dizygotic twins

• a triangle with connecting line = identical twins

Numvers in pedigree table meaning

teh roman numbers on th side refer to the generation they are in and the numbers underneath the people refer to the person soecifcally

crossing

the mating of two induvidual togther with differnt traist to produce a ceratin offsping with those traits

• indicated using X

what are the generations in crossing

P1 = parental generation

F1 = first filial generations

F2 = 2nd filial genereation

Pheontype

the physical manafestation of one genotype that refkect differnly based on dominant and recessive genes

• 1 gene = ratio of 3:1

genotype

the tarts that you hold genetically that you inherti from your parents

• aren’t always expressed physically

• 1 gene = ratio of 1:2:1

Homozygous vs heterozygous

Homozygous: have two copies of the same chromosome/ gene type ( same alleles)

Herterozygous Have two copies of differnt version og the gene / allele with only 1 being prsented

dominant vs recessive

Dominant: the allel that determine you phenotype even if another allele is present

Recessive: the allele that can only effect phenotyoe if a person have 2 copies and no dominant gene are present

who is gregor mendel

a man how used pea plants to understand how version of traits are passed down trhough generations

• used samples that differed in two traits , shape ( round or wrinkled) and colour ( yellow or green)

what is pure breeding

the breed of two homzygous indivudual with differnt trits

• leads tp the production of child with half of their gamete having one parnts trati and the on half having the other parent trait

• child will beheretozygous

Complete dominance

The inheritance of allele with one being dominant over the other

• dominant determines phenotype and rcessive onlydoes if two are present

incomplete dominance

Occurs when niether allel is particularly dominant over one another leading to the production of a hybrid species

• the phenotype will be differnt from bith parnts due to a combination of two equally dominant / recessive alleles

example of incomplete dominance

the crossing of a one flower with the dominant white colour gene and the other with a dominant red colour gene leading to the production of a pink flower with the genotype of one white gene and 1 red gene that may prodce whietred or pink offspring

otherreason for phenotype difernce

Phenotype differnt in plants may also be due to differnce in growing conditions

• lants that grown in differnt soil with differnt solute compositon may present with differnt colours

double heterozygous

an induvidua; with two set of heterozygous alleles for differnt genes that always produces 4 differnt ganete types - will have one dominant and 1 recessive allel from 2 differnt tratsits

independent assort of heterzygous individuals

due to independent assort ment when the gametes of a netrozygous individual align in coloum sof mother and father they will produce gamets with 1 dominant and one recessive gene from 1 parent

• if they a=have the alternative arrangement they will get an 2 dominant or two recessive alleles from each parent

ratios for 2 gene inheritence

phenotype: 9:3:3:1

Genotype: 1:2:1:2:4:2:1:2:1

Linked genes

Lnked gene are genes on the same chromosome that are inherited togther is meiosis

• discovered by thomas Hunt Morgan

• are only separeted in Recombination occurs

Morgans experimnet with drosophilia

mated Drosophilia whichis a common form of vinegar fly with only 4 pairs of chromose that could produce offspring within 2 weeks

• mated a fly with 2 mutation ( brown and regular wing) that were ofetn inherited tgther and 1 with out those mutation ( blcak and vestigial wings)

Morga epxriment results

lead to the production of a child with 1 chromsome with the muations and 1 chromomse withotu the muation

• produced the gamates with 1 haing the muated chromsome, 1 having the normal chromosome, and 2 with only one muation

crossing of linked genes

when linked gene are crossed / reconbined it leads to only 1 of allels that are inherited tigther form being present in the chromosomes of the persons gamete

Non-recmbinant vs recombinat progeny

Non-recombinat: children that will inherit the same combination of allel as their parents ( linked gne inherited togther) - more commom

Recombinant: chrildren that will inherit and new combination of allels that differs from their parnts with 1 chromomse contain genetic material from both parents( linked gene are not inherited togther) - less common and recombination is more rare

Autosomes

all other chrosomes that aren’t gender chromosomes

what is X linked inheritance

the inheritance of genes found on te X chromosme that aren’t always gendered

• the X chromoses has 1,100 genes while the Y chromosmes only have 78

• femals have 2 X chromosomes

• Males have 1 X and 1 Y chromosomes ( only have one chromosme fefcting their pehnotype)

X linked inheritance (recessive)

if both parent have the gene then both gender can be effected, if just the father tthe the female will be a carreier but not effect, if just the mother then just the only the son can inherit (especially if homozygous)

for a recssive trait to be inherited by a

• female the parnts must carry the gene so she can inherit the gene from both parents

• Male the mother must acrry the gene as th male will inherit a Y gene from his father so the effect X gene must come from the mother

X-linked inheritance ( dominant)

if the father has the gene then only the female child is effect ( male child will inherit Y), if the mother has the gene then the son will have it and the daught might deodning, if they both have the gene then either gender can get it

For a dominant X’linked chromsomes to be inherited by a

• female at least oe of their parenst must inherit the gene

• Male just the mother needs to be a carrier

carrier

a person who carries the gen for the mutation or disease but isn’t effect by it as the gene is recessive